98 LECTURE lY. 



tree of life, arbor vikv. The white fibres, called the crura 

 cerebelli, connecting the cerebellum with the eucephalon, are 

 sensitive ; not so the foliated parts. From all experiments 

 hitherto made, the cerebellum seems to be chiefly connected 

 with motion. If it be destroyed on one side only, paralytic 

 phenomena are observed, in which the body rolls towards the 

 opposite side ; if the whole cerebellum is destroyed, the verte- 

 bral column, and consequently the whole body, loses the 

 power of equilibrium, the animal oscillates, the walk resem- 

 bles that of an intoxicated person, all the motions are irregular 

 and without any harmony. The same facts are observed in 

 diseases in which the cerebellum is by any cause affected. The 

 relation of the cerebellum to the sexual functions, ascribed to 

 it by Gall, and which has become an axiom in phrenology, has 

 not been confirmed by experience. 



It results from these facts, that the examination of the cere- 

 bellum would contribute but little to the elucidation of the 

 questions before us, inasmuch as that part of the encephalon 

 cannot be proved to be connected with the intellectual functions. 



There remains now the brain proper, which constitutes by far 

 the largest mass of the encephalon, covering all other parts on 

 being viewed from above, and at once distinguished by the 

 singular convolutions on the surface. The cerebrum is divided 

 into two hemispheres by a process of the dura mater termed 

 thefalx. Another process of the same membrane, termed the 

 tentorium, extends horizontally between the cerebrum and the 

 cerebellum. Thus the cerebrum constitutes, as it were, a 

 separate whole which, as comparative anatomy teaches, has 

 overgrown and, so to say, suppressed all other cerebral parts. 

 This overgrowth increases in the lower animals accordingly as 

 they approach the human conformation. In the lowest verte- 

 brates, fishes, the cerebrum is only a grey knot, situated in front 

 of the other ganglia of the cerebral stem, and in the same line. 

 But the cerebrum swells out like an inflated india-rubber pouch 

 in the higher vertebrates, gradually covering the grey ganglia 

 of the primitwe brain, and the imperfectly arched forms of 

 the originally separated meso-cephalon, which are known by 

 the name of thalami o]jtici and tuhercula quadri(jemina; it then 



