1815.] On the Cerehelhm. M'f 



the chief organs of sense, is the seat of sensation, so we might 

 expect the cerebeUtun to be the organ of volition. This supposition 

 receives additional force from the consideration tliat, as the organs 

 of sense and the cerehellum are the first and the last portions of the 

 ner\'ous system ; so sensation and volition are the first and the last 

 of its functions. But this supposition is completely confirmed when 

 we recollect that the degrees of voluntary power always bear a close 

 analogy to the various magnitudes of the cerebellum." 



If we desire to listen to, or to look at, any object, the muscles 

 support the action of seeing and of hearing : hence sensation 

 and voluntary motion are not in opposition. It is also quite 

 erroneous to suppose that only the posterior nerves of the spinal 

 mass go to the muscles, and the anterior to the organs of sensation ; 

 and it is incorrect to. believe that almost all tlie parts of the body 

 have filaments of ascending and filaments of descending impres- 

 sions. The two roots of nerves of each lialf of the spinal marrow, 

 namely, the anterior and posterior, go to different parts of the 

 body; and it is erroneous to admit that filaments of the antciior 

 and posterior fasciculi of the spinal mass of nerves go to almost 

 every part : the muscles and skin of the back receive their nerves 

 from the posterior roots, whilst the muscles and skin of the 

 abdomen receive theirs from the anterior roots, and vet the 

 fore and back parts of the body have sensation and voluntary 

 motion. » 



Mr. Alexander Walker, in considering the cerebellum in opposi- 

 tion to the face has neglected to take any notice of the brain. Docs 

 lie therefore consider that part to have nothing to do with sensation 

 and volition ? 



The degree of voluntary power bears jio proportion with the size 

 of the cerebellum. 



Gall and Spurzheim have shown that the cerebellum in children 

 is much smaller in proportion than in the adult, and yet children 

 have more of muscular agility than adults. 



The large shark described in the Philosophical Transactions for 

 180f) and IHI,^, an animal said to have tlic greatest locomotive 

 power, has a remarkably minute cerebellum. See vol. an. I SOD, 

 pi. xix. fl, and pi. xx. ua. 



Swallows, which possess amazing locomotive powers, have a small 

 cerebellum ; and Cuvicr has shown (Le(;ons d'Anatomie Comp. 

 tom. ii. |). \W.\)y that the proportions of the cerebellum and 

 cerebrum in the bull and in man are absolutely the same, yet their 

 degree of voluntary power is very diflercnt. It is true that fishes 

 liave a larger eereijclUim in j)roportion to their brain, and that they 

 pfjssess a very strong locomotive power; and the rongeurs have 

 likewise a very large cerebellum ; and many of them, as the hare, 

 squirrel, ^c. possess a great locomotive power; but this is no 

 general priiicii)le. 



I shall lierc subjoin a few comparisons f)f tlie cerebellum and 



