MALPIGHI, MARCELLO

(b. Crevalcore, Bologna, Italy, baptized 10 March 1628; d. Rome, Italy, 29 November 1694)

medicine, microscopic and comparative anatomy, embryology.

Malpighi was the son of Marcantonio Malpighi and Maria Cremonini. In 1646 he entered the University of Bologna, where his tutor was the Peripatetic philosopher Francesco Natali. On Natali’s advice Malpighi in 1649 began to study medicine. He first attended the school conducted by Bartolomeo Massari, then that of Andrea Mariani; with Carlo Fracassati he was among the nine students allowed to attend the dissections and vivisections that Massari conducted in his own house.

Malpighi graduated as doctor of medicine and philosophy in 1653; three years later, still in Bologna, he began teaching as a lecturer in logic, but toward the end of the year he was called to the chair of theoretical medicine at the University of Pisa. The three years that he spent in Pisa were fundamental to the formation of Malpighi’s science. Influenced by Giovanni Alfonso Borelli, who was then professor of mathematics in the same university, Malpighi turned from Peripateticism to a “free and Democritean philosophy.” He also participated in animal dissections in Borelli’s home laboratory and, through Borelli, entered the scientific orbit of the school of Galileo, which was at that time best represented in Tuscany itself, in the Accademia del Cimento (1657–1667).

By 1659, however, Malpighi was no longer able to tolerate the Pisan climate. He therefore returned to Bologna to become extraordinary lecturer in theoretical medicine. Toward the end of 1660 he assumed the ordinary lectureship at the university in practical medicine. In 1662 he went to the University of Messina, where he held the principal chair of medicine; four years later he returned to Bologna to lecture in practical medicine again. A letter of 28 December 1667 asked him to undertake scientific correspondence with the Royal Society of London; Malpighi agreed, and the society subsequently supervised the printing of all his later works. In 1691 Malpighi was called to Rome as chief physician to Pope Innocent XII. He died there, in his apartments in the Quirinal Palace.

Malpighi’s first—and fundamental—work is the De pulmonibus, two short letters which he sent to Borelli in Pisa and which were published in Bologna in 1661. After his return to Bologna in 1659 Malpighi, together with Carlo Fracassati, continued to conduct dissections and vivisections. In the Course of these he used the microscope to make fundamental discoveries about the lungs, which he quickly announced in the letters to Borelli.

According to the traditional quaternary system, the lungs were fleshy viscera, endowed with a sanguine nature and hot-humid temperament. Having subjected them to microscopical examination, Malpighi found them to be an aggregate of membranous alveoli opening into the ultimate tracheobronchial ramifications and surrounded by a capillary network. He had thus discovered the connections, until then sought in vain, between the arteries and the veins. His observations were of basic significance for two reasons—the pulmonary parenchyma (and subsequently the other parenchymas) for the first time could be seen to have a structure, and the observation of the capillaries confirmed the theory of the circulation of the blood and assured its general acceptance.

Malpighi’s mastery of microscopic technique was apparent even in De pulmonibus. He used instruments of different magnifying powers and made observations with both reflected and transmitted light. He prepared Specimens in a number of ways, including drying, boiling, insufflation (of the tracheobronchial tree or of systems of blood vessels), vascular perfusion, deaeration (by curshing), corrosion, or a combination of these methods. In choosing to examine the frog, Malpighi was able to avail himself of the so-called “microscope of nature.” He was able to visualize, with a relatively small magnification, so minute a feature as the capillary (the capillary network itself is so fine in mammals that Malpighi was never able to observe it with the microscopes available to him). Malpighi acutely remarked that nature is accustomed “to undertake its great works only after a series of attempts at lower levels, and to outline in imperfect animals the plan of perfect animals.”

Malpighi saw the structure of the lung as air cells surrounded by a network of blood vessels; he interpreted this structure as a well-devised mechanism to insure the mixing of particles of chyle with particles of blood—in other words, for the conversion of chyle to blood (then called hematosis), a function that the Galenists attributed to the liver. Jean Pecquet had shown in 1647 that the chyle, instead of being conveyed to the liver, was introduced into the blood in the superior vena cava, at a point shortly before that vessel reached the heart, and was then distributed to the lungs through the pulmonary artery.

In the four years, 1662–1666, that he spent at the University of Messina, Malpighi enthusiastically continued his researches on fundamental structures, making use also of marine animals from the Strait of Messina. He published the results of these researches in a series of treatises in 1665–1666. These were devoted mainly to three major topics—neurology, adenology, and hematology.

The short works De lingua (Bologna, 1665) and De externo tactus organo (Naples, 1665) are closely linked to each other. In De lingua,Malpighi reported peeling two layers from the surface of the tongue—the horny layer and the reticular (or mucous) layer that is now named for him—and thus exposing the papillary body, in which he distinguished three orders of papillae. He speculated that these papillae could be reached through pores in the epithelium and thereby stimulated by “sapid” particles dissolved in the saliva, the organismal liquid the significance of which had been recognized just a few years previously by Nicholas Steno. It is easy here to recognize the influence of Galileo, who in ll saggiatore (1623) had suggested that the very small taste particles, when “placed on the upper surface of the tongue and, mixed with its moisture, penetrate it and carry the tastes, pleasant or otherwise, according to the differences in the touching of the different shapes of these tiny corpuscles, and according to whether they are few or many, faster or slower.”

Malpighi’s discovery of the sensory receptors—the papillae of the tongue were followed by the cutaneous (or tactile) papillae—formed part of a wider neuroanatomical research. In the treatise De cerebro, which was published in 1665 with De lingua, he dealt mainly with the white substance of the central nervous system, which he found to be composed of the same fibers that form the nerves. Malpighi conceived of these fibers as long, fine channels filled with a liquid—the nerve fluid—which was secreted by the cortical gray matter, or, more precisely, by the cortical glands. In his later treatise De cerebri cortice (1666), Malpighi claimed to have demonstrated these glands, but his results were in fact due to an artifact.

On the basis of his observations, whether true or false, Malpighi in any event succeeded in constructing a mechanism to encompass the entire neural course from the cortex of the brain to the peripheral endings of the nerves: the neuron, in which the transmission of the nervous impulse could be equated with the transmission of a mechanical impulse through a liquid mass in accordance with Pascal’s principle.

During his years in Messina, Malpighi made further investigations into the structure of another mechanism fundamental to his iatromechanical atomism: the gland, or secretion machine. The function of this mechanism was to select specific particles of blood brought by an afferent artery, to separate them from others flowing back through an efferent vein, and to introduce them, as an independent liquid, into an excretory duct. The sieve may thus be used as a convenient model (“cribrum” and “secretio” are even etymologically the same); it offers an a priori explanation of the operation of the secreting mechanism by postulating a proportionality of form and dimension between the pores and the particles to be separated. Malpighi certainly recognized that he could not investigate this “minima simplexque meatuum structura” directly, but he did not abandon his search for the mechanism that might contain the pores. This he localized, a priori, at the point at which the smallest ramifications of the artery, vein, and duct are joined together.

Malpighi continued to search for ever finer and more minute structures within the glandular parenchyma. These investigations were stimulated by the discovery of the pancreatic duct (by Wirsüng in 1642), the testicular duct (by Highmore in 1651), the submandibular duct (by Wharton in 1656), and the parotid duct (by Steno in 1660).

The secreting mechanism devised by Malpighi was based on a follicle that, on one hand, is continuous into the secretary tubule, and, on the other, is surrounded by the ultimate ramifications of the arteries, veins, and nerves. In passing from the artery to the vein, the blood channel and the contiguous glandular follicle are permeable to the particles that must be eliminated and impermeable to the particles that must be eliminated and impermeable to the particles of venous blood. By analogy with the sieve, and without invoking vitalistic arguments, secretion can thus be explained in purely mechanical terms. In De renibus Malpighi set down a series of convincing observations in support of his system. He skillfully made use of staining techniques by affusion to show the renal tubules, both straight and twisted, while by injecting coloring into the arteries he was able to demonstrate the tufts of vessels attached to the branches of the interlobular arteries. He believed, however, that the ampullar extremities of the renal tubules (the Malpighi corpuscles) were enclosed within the vascular tufts.

Malpighi reiterated and developed his theory of glandular structure in the epistolary dissertation De structura glandularum conglobatarum consimilique partium, dated June 1688 and published in London the following year. Although the “conglobate” glands of Sylvius—that is, the lymph nodes—are emphasized in the title, less than half the treatise is devoted to them. For the rest, Malpighi reported additional observations on glands that were already known and considerably expanded his earlier work on the secretary mechanism. He also included remarks on the glandular membranes (later classified by Bichat as serous and mucous).

Having established the capillary circulation and devised a mechanism to explain hematosis; having defined and systematized a nervous mechanism endowed with highly acute sensory receptors; and having postulated a secreting mechanism, Malpighi turned to an analysis of the blood—the universal fluid necessary to all these machines. His chief hematological treatise, De polypo cordis, appeared in 1666 (or 1668?) as an appendix to De viscerum structura.

“Heart polyps” had been identified for some time and with a certain frequency, especially in patients who had died from severe cardiorespiratory insufficiency. Previous researchers had explained such polyps in various ways, even invoking traditional humoral theory. Malpighi, however, considered these lesions to be the result of an intravitam process of coagulation, which had as its model the coagulation of blood extracted from the organism. The study of coagulum was thus fundamental, and culminated in Malpighi’s demonstration that the “phlogistic crust” was, despite its whitish color, derived from the whole blood that “confuses our poor eyes with its purple [color].” To this end he broke the blood down into its component parts (a method that he had successfully employed in his studies of viscera and organs) by continuing artificially in the coagulum the separation (into coagulum and serum) that occurs naturally when blood is extracted from an organism. Malpighi found that the coagulum, after repeated washings, “from being intensely red and black becomes white, while the water is reddened by the extracted particles of color.” The phlogistic crust thus corresponds in large part to the bleached-out coagulum; the difference between them is only quantitative (that is, it lies in the amount of coloring material that each contains) and not qualitative, as supposed by the humoral theory.

Microscopic examination of a clot of coagulum also enabled Malpighi to observe, as separate components, the interlacing white fibers that arise from the conglutination of much smaller but similarly shaped filaments (a process similar to that which occurs in the crystallization of salts) and the red fluid that fills the interstices of these meshes of fibers. With the microscope Malpighi could perceive that the red fluid was composed of a host of red “atoms”; it is thus clear that the discovery of the red corpuscles—although variously attributed by a number of authors who would seem to be unaware of their unmistakable description in the De polypo cordis—is surely Malpighi’s

Malpighi was able to utilize even a morbid deviation such as the heart polyp toward an investigation of a normal phenomenon. He studied aberrations to cast light upon normal organisms. In the same way, he studied simple animals to understand more complex ones, writing that the

study of insects, fish, and the first unelaborated outlines of animals has been used in this century…to discover much more than was achieved by previous ages, which limited their investigations to the bodies of perfect animals only.

Having stated this methodological formulation, Malpighi applied it in his work on the silkworm, De bombyce (London 1669), and in the latter embryological and botanical works that were edited by the Royal Society for publication in London in the 1670’s.

Malpighi was led to do embryological research through an analogy with the artisan who “in building machines must first manufacture the individual parts, so that the pieces are first seen separately, which must then be fitted together.” as he asserted in De formatione pulli in ovo (1673). In de bombyce, he had carefully observed the artisan nature construct each of the three stages—larva, chrysalis, and moth—through which the silkworm is formed. He further remarked on the specific apparatuses with which the silkworm is provided, among them the air ducts (tracheae) and the blood duct with a number of pulsating centers (corcula).

With the De formatione and the subsequent appendix to it (1675), Malpighi brought a fine structural content to embryology, which became a valuable aid to illustrating the morphology of the adult. So, too, the study of lower forms of life clarifies the morphology of more highly developed ones. Malpighi noted that the study “of the first unelaborated outlines of animals in the course of development” is particularly fruitful because the artisan nature forms them separately before combining them with one another. In the embryo, for example, the miliary glands, which will merge to form the liver, are still distinguishable as the cecal sacs (which in crustaceans remain distinct). From this point on, the paths of embryogenesis and phylogenesis were destined to cross.

The chick fetus develops in a manner similar to that of the plant embryo contained within a plant seed: from being enveloped at the start, it simultaneously “evolves” and grows in size as a result of the influx of food (yolk and albumen) liquefied by the warmth of the nest or by the fermentation process set in motion by fecundation. This notion, that embryogenesis consists of the development of constituents that in some sense existed prior to incubation, but which are nevertheless secondary to fecundation (see Adelmann), since they are induced by the “colliquamentum” of the pellucid area by the aura—or spiritous emanation —of the male seed, gave fuel to the doctrine of pre-formation, which then became a strong alternative to the traditional doctrine of epigenesis.

Malpighi’s chief embryological discoveries were the vascular area embraced by the terminal sinus, the cardiac tube and its segmentation, the aortic arches, the somites, the neural folds and the neural tube, the cerebral vesicles, the optic vesicles, the protoliver, the glands of the prestomach, and the feather follicles.

Malpighi clearly stated his comparative method in the introduction to Anatomes plantarum idea (1675):

The nature of things, enveloped in shadows, is revealed only by the analogical method [“cum solo analogismo pateat”]. Hence the necessity to follow it entirely, so as to be able to analyze the most complex mechanisms by means of simpler ones that are more easily accessible to the experience of the senses. It is the most important and most perfect things, however, that are the most immediately attractive to human genius, since they are the most necessary to human utility and therefore most worthy of consideration.

This had been true in the early work of even Malpighi himself. With youthful ardor, he had flung himself into the investigation of higher animals,

…but these, enveloped in their own shadows, remain in obscurity; hence it is necessary to study them through the analogues provided by simple animals [“simplicium analogismo egent”]. I was therefore attracted to the investigation of insects; but this too has its difficulties. So, in the end, I turned to the investigation of plants, so that by an extensive study of this kingdom I might find a way to return to early studies, beginning with vegetant nature. But perhaps not even this will be enough, since the yet simpler kingdom of minerals and elements should take precedence. At this point the undertaking becomes immense, and absolutely out of all proportion to my strength.

If Malpighi retreated before the demands of making a systematic study of minerals, he nonetheless undertook the study of plants with extraordinary success. Anatome plantarum, which appeared in London in two parts (1675 and 1679), earned him acclaim (along with Nehemiah Grew) as the founder of the microscopic study of plant anatomy. In his investigation Malpighi found that plants also have a mechanical structure: he described their ducts (some of which he compared to the tracheae of insects) and their basic “cellular” structure (an aggregate of “utricles”), which Hooke had already described (as “cellulae” in the Micrographia.

In his later studies Malpighi used the “Microscope of nature” as it was manifest in natural anomalies, and in particular in monstrosities and pathological aberrations. For example, he investigated warts and found the dermic papillae to be strikingly enlarged. Anomalous structures may be not only enlarged but also so arranged as to clarify individual components in the normal state. Thus, in onychogryphosis the lamellar structure of the normal nail is apparent; while in the jugular horn of a calf the reinforced projections of the papillae stand out, whereas in the normal horn they are concealed.

The correspondence between normal and anomalous horn is not only structural, but also morphogenetic, since the metamorphosis of the cutaneous strata into the horn is caused by mechanical stimulation. Under normal conditions this stimulation is exerted by the bony excrescence of the frontal bone: in the jugular horn it is the result of the irritation of the yoke and of the resulting saccate accumulation of fluid in the subcutaneous tissue. Malpighi adduced a similar mechanical morphogenesis in the polycystic kidney: the glandular follicles (Malpighi’s corpuscles) appear enlarged and distinct in this condition because they have been dilated by urostasis secondary to a blockage of the outflow channels. Similarly, in the nodules of the cirrhotic liver, the hepatic follicles are enlarged by the “microscope of nature,” as are lymphatic follicles that have been altered by disease (usually tuberculosis).

In De polypo cordis and subsequent treatises it is possible to identify explicit references to pathological material obtained during autopsy. Malpighi recognized the importance of local lesions, and his pathological investigations were considerably enhanced by the microscopic anatomy of the 1660’s, of which he himself was the most important investigator. The discovery of minute functional mechanisms, which in the aggregate give rise to the vital event, gave abnormal structures an added significance. The anatomical investigation of the breakdown of any of these mechanisms—even if only in such macroscopic equivalents as the lesions visible in the dissecting room — demonstrated the effect of such disturbances on the economy of the organism as a whole. Such clinical manifestations are proportional to the place and nature of the lesion; subtle anatomy thus gave rise to the anatomical investigation of the causes and localizations of disease (to paraphrase the title of the later work of Morgagni).

In his medical anatomy (or practical anatomy, as it was then called), in his emphasis on those aspects of anatomy proper to medical practice, and above all, in his use of anatomoclinical parallelism, Malpighi shaped the work of at least two generations. His pupils included Albertini and Valsalva; the De sedibus et causis morborum per anatomen indagatis of their pupil Morgagni represents a most important continuation of Malpighi’s work.

Malpighi also made considerable contributions to vegetable pathology. In particular he made a study of plant galls, which he found to be a morbid alteration of the structural plan of the infested plant. Finally, Malpighi wrote an important methodological work, De recentiorum medicorum studio, in which he supported rational medicine against the empiricists. Rational medicine was also the basis for his many Consultationes, which attest to the medical practice that he carried out concurrently with his biological researches.

BIBLIOGRAPHY

I. Original Works. Malpighi’s most important works are De pulmonibus observationes anatomicae (Bologna, 1661); De pulmonibus epistola altera (Bologna, 1661); Epistolae anatomicae de cerebro, ac lingua … Quibus Anonymi accessit exercitatio de omento, pinguedine, et adiposis ductibus (Bologna, 1665); De externo tactus organo anatomica observatio (Naples, 1665); De viscerum structura exercitatio anatomica … Accedit dissertatio eiusdem de polypo cordis (Bologna, 1666); Dissertatio epistolica de bombyce (London, 1669); Dissertatio epistolica de formatione pulli in ovo (London, 1673); Anatomes plantarum pars prima. Cui subjungitur appendix iteratas et auctas de ovo incubato observationes continens (London, 1675), which is prefaced by Anatomes plantarum idea, dated November 1671; Anatomes plantarum pars altera (London, 1679);“Dissertatio epistolica varii argumenti” [addressed to Jacob Spon], in Philosophical Transactions of the Royal Society of London, 14 (1684), 601–608, 630–646; Opera omnia (London, 1686; repr. Leiden, 1687); De structura glandularum conglobatarum consimiliumque partium epistola (London, 1689); Opera posthuma (London, 1697; repr Amsterdam, 1698); Consultationum medicinalium centuria prima (Padua, 1713); and Consultationm medicarum nonnullarumque dissertationum collectio (Venice, 1747), written with J. M. Lancisi.

A recent selection is Luigi Belloni, ed., Opere scelte (Turin, 1967), with an introduction containing a useful synopsis of Malpighi’s work.

II. Secondary Literature. A definitive biography is Howard B. Adelmann, Marcello Malpighi and the Evolution of Embryology (Ithaca, N. Y., 1966).

Luigi Belloni

MALPIGHI, MARCELLO (1628–1694)

MALPIGHI, MARCELLO (1628–1694), Italian physician and anatomist. Malpighi was born in Crevalcore, near Bologna, on 10 March 1628. He graduated in medicine and philosophy at the University of Bologna in 1653, and he taught logic at the same university until 1656, when he was called to the chair of theoretical medicine at the University of Pisa. Three years later he returned to Bologna, lecturing in theoretical and practical medicine. From 1662 to 1666 he held the chair of primary professor of medicine at the University of Messina. He then returned once more to Bologna, where he taught practical medicine until 1691, the year in which he moved to Rome in the capacity of chief physician to Pope Innocent XII. He died in Rome on 30 November 1694. These institutional settings are of a special importance in understanding his development as an anatomist, physician, and natural philosopher. Although he was trained at Bologna in the traditional course of scholastic disciplines, he also attended with other select students the private dissections and vivisections conducted by the university professor Bartolomeo Massari. In his time at Pisa he met Giovanni Alfonso Borelli (1608–1679), professor of mathematics there, and their ensuing collaboration was crucial in bringing Malpighi closer to corpuscularianism (the idea that the visible properties of matter derive from the interactions of minute particles of matter), to mechanical philosophy (the view that every natural phenomenon can be explained through matter and motion), and to Galileo's natural philosophy. In Messina he found a congenial environment for his investigations on marine animals and the sensory organs. Finally, from 1667, correspondence with Henry Oldenburg and the relationships that he established with the Royal Society brought Malpighi into closer contact with English experimental physiology.

Malpighi's works display a wide range of interests. In De Pulmonibus (On the lungs; Bologna, 1661), composed in the form of two letters addressed to Borelli, he announced his discovery of capillary circulation and gave a detailed account of the vesicular structure of the human lung. In Epistolae Anatomicae de Cerebro ac Lingua (Anatomical letters on the brain and the tongue; Bologna, 1665) and in De Externo Tactus Organo (The external organ of touch; Naples, 1665), he made his discovery of the sensory receptors of the tongue and cutaneous papillae part of a far-reaching project in neuroanatomical research. De Viscerum Structura (The structure of the internal organs; Bologna, 1666) and De Structura Glandularum Conglobatarum (The structure of the conglobate glands; London, 1689) present Malpighi's main theoretical view of the gland as the building block of the body's mechanical structure. In De Bombyce (On the silkworm; London, 1669) he investigated the anatomy of insects, and he gave an accurate description of the development of the chick in De Formatione Pulli in Ovo (The development of the chick in the egg; London, 1673), adding new evidence in support to the preformationist hypothesis, that is, the idea that the organism is already present and fully developed in the seed or egg. In Anatomes Plantarum (Anatomy of plants; London, 1679), Malpighi made use of the microscope and its related techniques in the study of animal and vegetable anatomy with great dexterity and profit. In De Polypo Cordis (On the polyp of the heart; 1666), he argued that the examination of pathological states, natural anomalies, and monstrosities could shed light on the normal functioning of organs and on the general processes of nature, thus laying the foundations for a research program centered on localizing the anatomical seats of disease.

From an anatomical point of view, Malpighi's work is a clear example of experimental investigation conducted in the wake of William Harvey's discovery of the circulation of the blood. Philosophically speaking, the main influence comes from Galileo's redefinition of matter, motion, and nature. Distancing himself from Descartes's extreme views on the mechanization of the body and the thorough identification of natural productivity with mechanical agency, Malpighi did not rule out the animate and sentient character of the body, and he emphasized the unattainability of perfection in the natural mechanics of living beings. Being both a theoretical anatomist and a physician—his Consultationes Medicinales (Medical consultations; Padua, 1713; Venice, 1747) are evidence of his clinical expertise—Malpighi represents the intriguing case of an early modern practitioner confronted with the need to harmonize theory (a new image of the body) and practice (the continuing success of traditional therapy) in the context of the new medical discourse.

See also Anatomy and Physiology ; Descartes, René ; Galileo Galilei ; Harvey, William ; Medicine ; Natural Philosophy ; Oldenburg, Henry .

BIBLIOGRAPHY

Primary Sources

Malpighi, Marcello. The Correspondence of Marcello Malpighi. Edited by Howard Bernhardt Adelmann. Ithaca, N.Y., 1975.

——. Opera Omnia. London, 1686. Rept. New York, 1975.

——. Opera Posthuma. London, 1697, Amsterdam, 1698.

Secondary Sources

Adelmann, Howard Bernhardt. Marcello Malpighi and the Evolution of Embryology. Ithaca, N.Y., 1966.

Bertoloni Meli, Domenico, ed. Marcello Malpighi: Anatomist and Physician. Florence, 1997.

Guido Giglioni

Marcello Malpighi

The Italian microscopist Marcello Malpighi (1628-1694) was the first to see the capillaries and was a founder of histology, embryology, plant anatomy, and comparative anatomy.

On March 10, 1628, Marcello Malpighi was born at Crevalcore near Bologna. He attended the University of Bologna, where he graduated in philosophy and in medicine in 1653. Malpighi became a lecturer in logic at Bologna in 1655 but left in 1656 to be professor of theoretical medicine at Pisa. There he met Giovanni Borelli, a mathematician who had recently turned his attention to the analysis of movement in animals.

Malpighi returned to Bologna in 1659, where he was made extraordinary lecturer in theoretical medicine. Through Borelli's influence, Malpighi was elected to the first chair in medicine at Messina in 1662, but in 1666 he returned to Bologna to become professor of medicine, and he remained there for the next 25 years.

By 1667 Malpighi's work had already aroused the interest of the recently formed Royal Society in London, and one of its secretaries wrote to him suggesting that he communicate his results to the society. Malpighi responded favorably, and most of his later books were published in London. He was elected a foreign member of the Royal Society in 1668.

Malpighi was also a successful physician, and in 1691 he became the personal physician of Pope Innocent XII in Rome. Malpighi died on Nov. 29, 1694, in Rome.

Discovery of Capillaries

In September 1660 Malpighi began to study the structure of the lungs, and within nine months he had communicated the results of these studies in two letters to Borelli in Pisa, who published them under the title De pulmonibus observationes anatomicae (1661). Malpighi presented "a few little observations that might increase the things found out about the lungs." These observations included the first descriptions of the air sacs (pulmonary alveoli) in the lungs of a dog and of the pulmonary capillaries in the frog and tortoise.

Having convinced himself of the presence of direct connections between the arteries and veins in the lungs of the frog and the tortoise, Malpighi was prepared to speculate that the same was so in other animals: he was unable to see such anastomoses in the dog's lung, perhaps, because these "small vessels escape the senses on account of their smallness."

Histological Studies

The science of the study of the structure of tissues was established by the classical microscopists, and Malpighi's contributions were among the most important. He published four tracts in 1665. The first one described the presence of "red globules of fat" in the blood vessels of the mesentery of the hedgehog. This is one of the earliest descriptions of the red blood cell, although Malpighi did not realize the significance of his observation. In other tracts he described the papillae of the tongue and the skin and suggested that these may have a sensory function. The layer of cells in the skin now known as the Malpighian layer was also described. The last tract of 1665 concerned the general structure of the brain. Malpighi showed that the white matter consists of bundles of fibers which connect the brain with the spinal cord. He described the gray nuclei that occur in the white matter.

Malpighi's De viscerum structura execitatio anatomica (1666) gives a detailed and fairly accurate account of the structure of the liver, spleen, and kidney. Malpighi dissected the tissue under the microscope, and he identified small particulate masses or "lobules," resembling bunches of grapes, in the liver. Each lobule was composed of "tiny conglobate bodies like grape seeds" connected by central vessels. Having seen these lobules in the livers of several species, he concluded that the lobule was the fundamental hepatic unit. He believed that the lobules were supplied by fine blood vessels and that their function was secretory. Malpighi realized, therefore, that one function of the liver is as a gland and that the bile duct must be the passage through which the secreted material (bile) passes: the gall-bladder was, therefore, not the site of origin of bile. He was also able to prove in an animal experiment that the gallbladder is only a temporary store for bile on its way to the intestine. Malpighi speculated that bile might be useful in the process of digestion.

Although Malpighi was fond of describing many structures as "glands," he realized, from his study of the blood supply to the spleen, that this organ is not a gland but a contractile vascular organ. He was the first to describe the lymphatic bodies (Malpighian corpuscles) in the spleen.

Whereas other anatomists believed that the outermost part of the kidney was structureless, Malpighi showed that it is composed of many little wormlike vessels (the renal tubules) which he called "canaliculi." Although he could not demonstrate any continuity between the convoluted canaliculi and the straight tubules in the central mass of tissue (medulla), he predicted that such a continuity exists. Malpighi's description of how he discovered the glomeruli in the outer part of the kidney is vivid: "In all kidneys which up to this time I have been able to get, I have detected a number of very small glands [that is, Malpighian corpuscles, or glomeruli]. In order to see these glands, black fluid mixed with spirit of wine should be injected through the renal artery. And when the kidney is sectione…. one will see these same innumerable glands attached like apples to the blood vessels, the latter swollen with the black liquid and stretched out into the form of a beautiful tree." Malpighi realized that the "glands" were connected to the "extreme ends of the arteries" and to the veins but did not observe the true nature of the "glands," that is, that they are composed of a tuft of capillaries. He speculated that their function was to secrete the urine.

Malpighi's detailed description of the medulla of the kidney showed how the canaliculi converge on the pelvis and enter the ureter. In pathological specimens he observed the formation of kidney stones in the pelvis.

Insect Anatomy

Malpighi's memoir De bombyce (1669), on the silk-worm moth, was the first detailed account of the structure of an invertebrate. Prior to his study, it was still believed that such small creatures were devoid of internal organs, and he himself was surprised to find that the moth was just as complex as higher animals. He not only discovered the trachae and spiracles, the system of tubes and holes through which insects breathe, but also correctly guessed their function. He was the first to describe the nerve cord and ganglia, the silk glands, the multichambered heart, and the urinary tubules, which still bear his name.

Embryological Studies

With his microscope, Malpighi was able to study much earlier stages of the embryo than had hitherto been possible. His results were communicated to the Royal Society in two memoirs: De formatione pulli in ovo (1672) and De ovo incubato (1675), which placed embryological study on a firm basis of sound observation. He saw the heart within 30 hours of incubation and noticed that it began to beat before the blood reddened. He described the development of the dorsal folds, the brain, the mesoblastic somites, and structures which were later identified as gill arches. However, Malpighi believed that he had seen the form of an embryo in an unincubated egg. A possible explanation is that the egg, being 2 days old, had been "incubated" in the hot Italian August sun. This observation was used, not by Malpighi himself as much as by his followers, to support the doctrine of preformation, that is, that the whole adult was present in the egg and had only to be "unfolded" by a suitable stimulus.

Plant Anatomy

Some of Malpighi's most extensive writing, beautifully illustrated, is on plants. Malpighi and his contemporary Nehemiah Grew became the confounders of plant anatomy by their systematic studies on the microscopic structure of plants. Malpighi's book Anatome plantarum was published in two parts in 1675 and in 1679. His illustrations frequently show the plant cell with its wall, first described by Robert Hooke in 1665.

Malpighi's interest in the structure of plants began when he noticed the broken branch of a chestnut tree which had fine threads projecting from the surface. Upon examining these with his lens he was struck with their resemblance to the air tubes of insects. Although he wrongly concluded that they served the function of breathing, his enthusiasm for the study of plants had been awakened. His drawings of the stems of higher plants distinguished between the annular rings of the dicotyledon and the scattered bundles of the monocotyledon (the terms dicotyledon and monocotyledon were introduced in the early 18th century). He suggested that material required for growth of the plant was formed from the sap by the leaves, but the erroneous idea that the sap circulated, as blood did, was originated by other writers.

Malpighi's work on the development of plants is just as significant as that on the development of animals. He made drawings of the embryo sac and endosperm and gave a superb account of the germination of seeds in which he differentiated between those later called monocotyledons and dicotyledons. He was the first to describe tubercles on leguminous roots, and he showed that some galls contained a grub. He traced the grub back to an egg and onward to an insect, of which he illustrated the egg-laying apparatus.

Further Reading

Some biographical information on Malpighi is in Howard B. Adelmann, Marcello Malpighi and the Evolution of Embryology (1966), and in Circulation of the Blood: Men and Ideas, edited by Alfred P. Fishman and Dickinson W. Richards (1964). For background see Charles Singer, A History of Biology to about the Year 1900 (1931; 3d rev. ed. 1959).

Additional Sources

Malpighi, Marcello, The correspondence of Marcello Malpighi, Ithaca N.Y. Cornell University Press, 1975. □

Malpighi, Marcello

3/10/1628–8/29/1694
ITALIAN
PHYSICIAN

In the second half of the seventeenth century, Marcello Malpighi used the newly invented microscope to make a number of important discoveries about living tissues and structures, earning himself enduring recognition as a founder of scientific microscopy, histology (the study of tissues), embryology, and the science of plant anatomy.

Malpighi was born at Crevalcore, just outside Bologna, Italy. The son of the owners of a small plot of land, Malpighi studied medicine and philosophy at the University of Bologna. While at Bologna, Malpighi was part of a small anatomical society headed by the teacher Bartolomeo Massari, in whose home the group met to conduct dissections and vivisections. Malpighi later married Massari's sister.

In 1655 Malpighi became a lecturer in logic at the University of Bologna. One year later, he assumed the chair of theoretical medicine at the University of Pisa. In 1659 he returned to Bologna as lecturer in theoretical, then practical, medicine. From 1662 to 1666 he held the principal chair in medicine at the University of Messina. Finally, in 1666, he returned again to Bologna, where he remained for the rest of his teaching and research career. In 1691, at the age of sixty-three, Malpighi was called by his friend Pope Innocent XII to serve as the pontiff's personal physician. Reluctantly, Malpighi agreed and moved to Rome, where he died on November 29, 1694, in his room in the Quirinal Palace.

Early in his medical career, Malpighi became absorbed in using the microscope to study a wide range of living tissue—animal, insect, and plant. At the time, this was an entirely new field of scientific investigation. Malpighi soon made a profoundly important discovery. Microscopically examining a frog's lungs, he was able for the first time to describe the lung's structure accurately—thin air sacs surrounded by a network of tiny blood vessels. This explained how air (oxygen) is able to diffuse into the blood vessels, a key to understanding the process of respiration. It also provided the one missing piece of evidence to confirm William Harvey's revolutionary theory of the blood circulation: Malpighi had discovered the capillaries, the microscopic connecting link between the veins and arteries that Harvey—with no microscope available—had only been able to postulate. Malpighi published his findings about the lungs in 1661.

Malpighi used the microscope to make an impressive number of other important observations, all "firsts." He observed a "host of red atoms" in the blood—the red blood corpuscles. He described the papillae of the tongue and skin—the receptors of the senses of taste and touch. He identified the rete mucosum, the Malpighian layer, of the skin. He found that the nerves and spinal column both consisted of bundles of fibers. He clearly described the structure of the kidney and suggested its function as a urine producer. He identified the spleen as an organ, not a gland; structures in both the kidney and spleen are named after him. He demonstrated that bile is secreted in the liver, not the gall bladder. In showing bile to be a uniform color, he disproved a 2,000-year-old idea that the bile was yellow and black. He described glandular adenopathy, a syndrome rediscovered by Thomas Hodgkin (1798–1866) and given that man's name 200 years later.

Malpighi also conducted groundbreaking research in plant and insect microscopy. His extensive studies of the silkworm were the first full examination of insect structure. His detailed observations of chick embryos laid the foundation for microscopic embryology. His botanical investigations established the science of plant anatomy. The variety of Malpighi's microscopic discoveries piqued the interest of countless other researchers and firmly established microscopy as a science.

see also Microscope, comparison; Microscopes.

Marcello Malpighi

1628-1694

Italian Physician and Biologist

Marcello Malpighi was an Italian physician and biologist who pioneered experimental methods to study living organisms with the aid of the newly invented microscope, thereby founding the science of microscopic anatomy. After Malpighi's contributions, microscopic anatomy became essential for advancing the fields of physiology, embryology, and medicine. He is often called the father of histology (the microscopic study of tissues) because of his work with tissue and cell samples. He helped to change many of the antiquated ideas regarding medicine with his discoveries. As an example, he was the first to demonstrate that capillaries connect small arteries and veins, completing the circuit of blood at the tissue. This discovery provided the factual data to support English physician Willam Harvey's (1578-1657) groundbreaking and controversial theory of the circulation of blood (1628). For almost 40 years Malpighi used the microscope to describe the major types of plant and animal structures, having significant impact on future generations of biologists. Moreover, his lifework brought into question the prevailing concepts of body function. His enemies, who failed to see how his discoveries could possibly improve medical practice, were vigorously opposed to the work of Malpighi. However, he was correctly convinced that microscopic anatomy would prove to have significant value and influence on medicine.

Malpighi was born in Crevalcore on March 10, 1628. He entered the University of Bologna at the age of 17. He was the oldest of eight children and lost both of his parents at the age of 21, prior to completing his education. He placed his career on hold for two years while he settled the affairs for the family. When he returned to his studies, he received a degree in medicine in 1653. Three years later he became a professor at the University of Bologna.

Malpighi questioned the prevailing medical teachings at that time, especially the reliance on the writings of the ancient Greek doctor Galen (130?-200?). He performed experiments that attempted to explain anatomical, physiological, and medical problems of the day in a different light. He was one of the first scientists to recognize the importance and value of the microscope in medicine. In 1661 he identified and described capillaries, which was one of the major discoveries in the history of science. Malpighi's views evoked increasing controversy and dissent, mainly from envy, jealousy, and lack of understanding on the part of his colleagues. Because of this, Malpighi bounced between various institutions of higher learning throughout his entire lifetime.

In 1662, Malpighi accepted a professorship in medicine at the University of Messina in Sicily. It was during this time that he identified taste buds and described the minute structures of the brain, optic nerve, and fat reservoirs. In 1666 he was the first to identify red blood cells and to attribute the color of blood to them.

After four years at Messina, Malpighi returned in 1667 to Bologna, where, during his medical practice, he studied the microscopic subdivisions of specific living organs, such as the liver, brain, spleen, and kidneys, and of bone and the deeper layer of the skin that now bears his name (called the Malpighian layer). Malpighi's work at Messina attracted the attention of the Royal Society in London; in 1669 Malpighi was named an honorary member, the first such recognition given to an Italian. Malpighi continued to make huge contributions to the field of microscopy. Not just confining his work to medicine, he studied insect larvae and plants and published a historic work in 1673 on the embryology of the chick.

Malpighi's ideas were considered extremely controversial, and in 1684 his villa was burned, his apparatus and microscopes shattered, and his papers, books, and manuscripts destroyed. He accepted an invitation from Pope Innocent XII (1615-1700) in 1691 to become the papal archiater (personal physician), a position that he held until his death in 1694.

JAMES J. HOFFMANN