Jan Evangelista Purkinje

1787-1869

Czech Physiologist and Histologist

Jan Evangelista Purkinje made pioneering contributions to histology and physiology. His observations led to many important insights into the workings of the human body, especially various visual phenomena. He invented the microtome, an instrument that slices tissues into very thin samples, and demonstrated the importance of technical advances in microscopy for biological research. In addition to Purkinje cells, his name has been given to identify specific types of conduction, fibers, figures, layers, networks, phenomenon, systems, and Purkinje-Sanson images. Although he made some of the earliest observations of the cell nucleus, the characteristics of cells, and cell division, other scientists are generally credited with these discoveries. He introduced the term "protoplasm" to describe the contents of cells.

Purkinje, whose parents were Czech, was born in Libochowitz, Bohemia. He was educated by Piarist monks and intended to join the order, though went instead to Prague to study philosophy. This led him to a deep interest in science and medicine. His graduation thesis on subjective aspects of vision, completed at the University of Prague in 1818, brought him considerable attention. Purkinje observed that when the intensity of illumination decreases, objects of different color but equal brightness appear to be unequally bright; this is now known as Purkinje's phenomenon or shift. In other words, blue objects appear brighter than red objects in dimmer light. He also described the threefold images of an object that are seen by an observer in the eye of another person. These images are caused by an object reflecting from the cornea's surface and both sides of the lens. This phenomenon is now known as "Purkinje's images." Johann Wolfgang von Goethe (1749-1832) was impressed by Purkinje's research on vision and the two became friends. In 1820 Purkinje studied the induction of vertigo that occurs when the body is rotated in an erect position, but he was unable to explain the phenomenon. In 1823 he was appointed to the Chair of Physiology at Breslau, where he founded an institute for histological research. Because university officials were unwilling to meet his demands for space and equipment, much of his research and teaching was carried out in his own home laboratory, which became known as the cradle of histology. Purkinje was highly respected as a teacher as well as a researcher. He accepted the Chair of Physiology at Prague in 1849, and established another institute for histological research. He directed research at the institute until his death in 1869.

In 1839 Purkinje was the first to use the term "protoplasm" in a scientific sense. Theologians had used the word protoplast for Adam, that is, "the first formed." As a physiologist, Purkinje used the term to refer to that which was first produced in the development of the individual plant or animal cell. Apparently, independent of Purkinje, Hugo von Mohl (1805-1872) used the word protoplasm to describe the part of the plant cell within the cell membrane. Although Purkinje's observations of the cell nucleus, or germinal vesicle, in the eggs of birds in 1825 preceded those of Robert Brown (1773-1858), he did not publish these studies until 1830.

Purkinje emphasized the value of microscopy, especially the new achromatic microscopes, and developed several innovative teaching tools and a knife that was a precursor of the microtome. He also established the use of balsam sealed preparations and adapted Louis J.M. Daguerre's methods to produce the first photographs of microscopic materials. During the 1830s Purkinje conducted numerous studies of microscopic structures, including studies of the skin of various animals, ciliary motion, nerve cells, myelinated nerve fibers, the large flask-shaped cells with numerous dendrites in the cerebellar cortex (now known as Purkinje cells), the unusual muscle fibers found below the endocardium in a specific region of the ventricles of the heart (the fibers of Purkinje) which are important in the conduction of the cardiac impulse, and so forth. In 1850 he was elected a Foreign Member of the Royal Society.

LOIS N. MAGNER