Lapicque, Louis

(b. Épinal, France, 1 August 1866; d. Paris, France, 6 December 1952),

physiology, anthropology.

Lapicque’s father, a veterinary surgeon, fostered his son’s inclination toward natural science. At the Paris Medical School, Lapicque displayed an active interest in physics and chemistry, which in those days was rather unusual in medical circles. He was therefore entrusted by the celebrated clinician Germain Sée to organize a small chemical laboratory in the HôtelDieu Hospital, where he investigated the circulation of iron in vertebrates. The amounts of metal to be measured being very small, he tried colorimetric tests. Such tests, despite their sensitivity, were then in disfavor because of their lack of accuracy. Lapicque succeeded in making the thiocyanate test for ferric iron a very precise tool that remained in general use for several decades. He showed that at birth iron is localized mainly in the liver, while there is none in the spleen. When pathological conditions bring severe destruction of red cells, iron accumulates in spleen and liver tissue in the form of a red pigment constituted essentially of colloidal ferric hydroxide. These results were published in his thesis for the doctorate in science. Lapicque’s experimental work was then interrupted. A Mme Lebaudy, the wife of a sugar magnate, wanted her son to take a world cruise on her yacht Semiramis with a group of dedicated young scientists who might inspire him. The son failed to embark, but the cruise proceeded as planned. Lapicque proved to be an active anthropologist. In the lands of the Indian Ocean he endeavored to measure the anthropological characteristics of the various groups of Negritos. He devised a very useful index: the radius-pelvic ratio, which allowed him to conclude that in ancient times a single Negro race was distributed from Africa to Oceania.

Lapicque made an extensive study of the relation brain and body weight, a relation discussed by Eugène Dubois, the discover of Pithecanthropus erectus. Lapicque, however, generalized this relation. The “exponent of relation” is the same not only between mammals but also between birds. The results appear most strikingly on logarithmic coordinates. The different animal species, even the fossil ones, are represented on parallel lines, the level of each defined by “the coefficient of cephalization” which represents the degree of nervous organization and, in a striking manner, the presumed intelligence of the species. Lapicque also found a precise relation between brain and eye weight.

Lapicque’s essential work, however, was in the general physiology of the nervous system. From 1902 he investigated the time factor in nervous processes. From this study he soon derived a fundamental concept: the functional importance of the time factor of nervous electrical excitability. He made it possible to express excitability precisely in terms of “rheobase,” an intensity factor, and of “chronaxie,” a time factor. Chronaxie represents the functional rapidity of the tissue under investigation. Slow muscles and nerves are characterized by a long chronaxie and fast muscles and nerves by a short one. Furthermore, chronaxie measurements, for the first time, numerically expressed the effects of many agents: for instance, temperature, drugs, and anesthetics. The chronaxies of motor nerves in man could be obtained, thus permitting the evolution of degenerative or regenerative processes to be followed quantitatively. Chronaxie also reveals the fine details of motor organization.

As early as 1907 the concept of the functional role of the time factor of nervous processes, expressed by chronaxie, led Lapicque to theoretical speculations. He postulated that the activation of a chain of nerve cells depended upon the successive electrical stimulation of each cell by the impulse or action potential of the preceding one. By using an electrical stimulus having a showed that there is such a stimulus of optimal duration defined by the chronaxie of every tissue investigated. In other words, this is selective excitation realized by a tuning between duration of stimulus and chronaxie. Thus Lapicque proposed a theory of nervous processes that was analogous in its principle to the tuning or resonance between two oscillating radio circuits. The theory indicated that transmission of excitation between two nerve cells was optimal when the cells had the same chronaxie. When the second cell had a long chronaxie, its excitation required iterative activation of the first. In that case the numerical expressions derived by Lapicque are adequate regardless of whether transmission depends on electrical stimulation or, according to successive “quanta” of a chemical mediator such as acetylcholine. Lapicque’s theory was first met with widespread approval and later encountered strong criticism. Yet even in recent years it has provoked much research. It correlated many unexplained results at a time when nervous processes could be investigated only by the indirect methods of electrical stimulation. When th e responses of nerve cells and fibers became directly accessible through modern electronics, several predictions based on Lapicque’s theory were confirmed. For instance, in 1913 Lapicque and Renè Legendre had shown that chronaxie of motor fibers or axons is in inverse ratio to their diameter. Thus the velocity of their impulse was assumed to be proportional to their diameter, which was demonstrated by the cathode–ray oscillographic records obtained by Gasser and Erlanger in 1928.

Lapicque’s activity was fruitful in many other areas. In nutritional physiology he added to the notion of isodynamic nutrients, developed by Rubner, a new concept: the margin of thermogenesis. His competence in that domain was amply used during World War I by the authorities responsible for the food supply of France. He was the first to advocate, in exceptional circumstances, the reduction of livestock to save grain that could be used for human consumption. This suggestion met with considerable opposition but was finally supported by the government. In connection with saving grain Lapicque found that certain seaweeds (Laminaria), collected in the proper season and correctly prepared, made an excellent oat substitute for the feeding of horses. He also investigated the physiology of marine algae. He discovered that ionic exchanges between the cell medium and the surrounding seawater proceed against an osmotic gradient, through the expenditure of metabolic energy. This process, involving an ionic “pump,” he named “epictesis,” akin to the modern concept of active transport.

As the field surgeon of an infantry regiment, Lapicque devised an adequate defense against the first attacks by poison gas: a filter of loose earth at the entrance of a trench shelter absorbed the gas. Unfortunately, this simple device was inefficient against the mustard gas later used by the German army. Lapicque always showed an unyielding and active opposition to any form of subjugation. In his late seventies he was jailed by the Gestapo for two months during the severe winter of 1941-1942.

Lapicque was an excellent sailor. Every summer he expertly navigated a twenty–ton yawl named Axone in the difficult waters off northern Brittany. The members of his laboratory were often board, enjoying his teaching, which combined physiology enjoying his teaching, which combined physiology and seamanship. He held perestigious teaching posts: associate professor at the Sorbonne in 1899, professor of general physiology at the Muséum d’Histoire Naturelle in 1911, and at the Sorbonne from 1919 to 1936. Both chairs had been Claude Bernard’s. Lapicque’s activity was not curtailed by his retirement; he studied many problems, such as the density of nerve cells in the various centers. Until his last days he gladly gave his extensive and diverse scientific experience to his students.

BIBLIOGRAPHY

1. Original Works. Lapicque’s writing include Observations et expériences sur la mutation du fer chez les vertébré, his Thése de sciences (Paris, 1897), “Unité fondamentale des races d’hommes à peacu noire. Indice radio–pelvien,” in Comptes rendus de l’Académie des sciences,. 143 (1906), 81-84; “Échantes nutritifs des animaux en fonction du poids corporel” ibid.,172 (1921), 1526-1529; “Mécanisme des échange entre la cellule et le milieu ambiant,” ibid.,174 (1922), 1490-1492; L’excitabilité en fonction de temps; la chronaxie, sa signification et sa measure (Paris, 1926); “Le poids du cerveau et i’intelligence,” in g. Dumas, Nouvea traité de psychologie,I (Paris, 1930), 204; “Leprobléme du fonctionnement nerveux. Esquisse d’une solution,” in G. Dumas, Nouveau traitÉ de psychologie, I (Paris, 1930), 147n–204; and La machine nerveuse (Paris, 1943), part of which was written during his imprisonment by the Germans.

II. Secondary Literature. See G. Bourguignon, La chronaxie chez l’homme (Paris, 1923); and A. Monnier L’excitation électrique des tissus. Essai d’interpretation physique (Paris, 1934).

A. M. Monnier