About this time, too, Casserius and others studied the auditory apparatus and described the ossicles, the small muscles of the internal ear, and the semicircular canals; they even followed the acoustic nerve. By the researches of a number of French and Italian anatomists it was likewise{163} established that the true seat of hearing lies within the internal ear, the external parts being merely of assistance in conducting sound. Thomas Willis was one of the first to consider the brain as an assemblage of organs and to assign special functions to certain of its divisions; he thus became a pioneer in cerebral localization, although most of his conjectures were inaccurate or fanciful. The workings of the brain were also studied by Pinel and others, who observed that in certain conditions of mania or partial insanity some of the mental faculties--such as memory, judgment, imagination, or will--were abolished or suspended, while other faculties were preserved; hence it was inferred that each faculty must have its own seat. The views thus enunciated were carried to an absurd degree by Gall, and later by Spurzheim, who made an entirely new classification, believing the cranium to be molded in a reasonably exact manner upon the brain, and that, by inspection of the exterior, the character of a given individual could be read. They thus founded the pseudoscience denominated phrenology, which we now know has practically nothing to justify itself. About the middle of the seventeenth century Glisson (a professor in the University of Oxford) recognized a property pertaining to all living tissue, which he termed irritability, and which he regarded as sufficient cause for all the phenomena of life; he enunciated certain views that, in times past, have had an important bearing upon the pathology of disease, but which were forgotten for sixty years or more until revamped by the Dutch anatomist, Goerter. It was the latter, with the great Haller, who, by a series of very ingenious experiments, elevated the suppositions of Glisson to the dignity of demonstrated facts. In 1747 the results of Haller's researches were published under the modest title of _First Lines in Physiology_; the author was, in fact, the great exponent of the doctrine of irritability in{164} neurophysiology, and for this deserves to be remembered wherever the history of our art is spoken of. This theory of irritability was applied to pathology by Fabre, of Paris, who refuted the mechanical theory of Boerhaave on inflammation, proving that the latter proceeds not from obstruction of the capillaries, but from exaltation of their irritability. It was also applied in many ways by Bichat, who enjoyed a brief, though memorable, career. The theory of irritability, along with the truths established by John Hunter in his researches on the blood, made a very distinct advance in the physiological knowledge of the seventeenth century, and the researches of those who contributed so much