SEVENTEENTH AND EIGHTEENTH CENTURIES 1 49 

 for his loyal conduct. This appointment, however, he did not retain for long, 

 but he moved to London and again set up in practice; there he made a great 

 reputation, became a member of the Royal Society, and published several 

 treatises. He has been described as an honest man of firm character, towards 

 the end of his life not very popular at court, owing to his outspoken criticism 

 of its corrupt morals. He died in 1675. 



Willis's principal work is his investigation of the anatomy of the brain 

 and the nervous system. His exposition of the structure of the brain and of 

 the nerves proceeding directly therefrom is the first that may be said to ful- 

 fil modern requirements; to his description of the outward configuration of 

 these parts posterity has had very little to add. He performed a still further 

 service to science in having paid special attention not only to the human 

 brain, but also to that of other vertebrates: in the introduction to his work 

 he expressly points out that comparative anatomy alone can provide a fully 

 satisfactory explanation of the structure and functions of the organs. The 

 account of his investigations into the brains of different animal forms is 

 illustrated with very fine engravings, a number of which were drawn by his 

 friend, the famous architect. Sir Christopher Wren, the designer of St. 

 Paul's Cathedral in London. With regard to the functions of the nervous 

 system, Willis, in contrast to the Aristoteleans Harvey and Glisson, asso- 

 ciated himself entirely with the theory advanced by Descartes. The manifesta- 

 tions of life are induced by currents in the nervous system, which penetrate 

 the brain and according to their nature are distributed into the different parts 

 thereof; the world of ideas and the memory he places in the cortex of the 

 great brain. Willis thus forestalls Swedenborg's radical investigations into 

 the localizations in the brain, which are certainly considerably deeper and 

 more detailed than his precursor's. Willis also carefully studied the func- 

 tional spheres of the different nerves; thus, by binding up the vagus nerve in 

 a live dog, he established their influence on the lungs and heart. 



In a work published at a later date Willis deals with the soul of animals. 

 This work has a far wider range than its title implies, for it contains a mass 

 of information of various kinds. Thus, he gives an account of a number of 

 investigations he made into the anatom^y of invertebrates, which would 

 have been of interest to his age had not at the same time Malpighi and 

 Swammerdam given far better accounts. The main purpose of the work, how- 

 ever, is a comprehensive study of the vegetative and sensitive soul, which in 

 his view — and in that of Descartes — is common to the animals and man. 

 Man has, indeed, his rational soul as well, which is immaterial and can there- 

 fore survive after death; the soul under discussion here is, on the other hand, 

 that material vital spirit which finds expression in currents in the nervous 

 system and which produces all the manifestations of life in animals and those 

 that are purely animal in man. How it happens that animals can in some cases 



