functions of the Cerebellum. 619 



perior to all other mammals except man. Man is excelled by many 

 other animals in one form or another of muscular activity ; a hound can 

 outrun him, a squirrel can outclimb him, a kangaroo can outjump him, 

 a fish can outswim him, and he cannot at all compete with a bird in fly- 

 ing. In the use of his fore limbs, however, he is far in advance of all 

 of them, and although he cannot fly, the versatility of his movements 

 is much greater than that required for flight. His cerebellar develop- 

 ment is greatly in excess of that of any other animal. In the human 

 race, the cerebellum develops with the greatest rapidity during early 

 childhood, the period in which the greatest number and variety of 

 muscular combinations are being practiced ; the period in which our 

 race most resembles the ape in all these and other particulars. 



In all those animals which begin to use their muscular powers as soon 

 as born, the cerebellum is well developed at birth. A chick only a few 

 hours old can peck at a June-bug with very accurate aim, and, as shown 

 in fig. 301, its cerebellum is then well developed. 



Experiments on individual animals bear out the theory that co-ordina- 

 tions of muscular stimuli take place in the cerebellum. It is possible, 

 in many cases, to remove either the cerebellum or the cerebrum without 

 immediate destruction of life. When the cerebrum alone is taken away, 

 the power of muscular movement is not destroyed, as the experiments 

 with the frogs, mentioned in chap. 60, prove. The same experiments 

 have been made upon all classes of vertebrates with practically the same 

 result. A bird deprived of the cerebrum loses its sensibility, or the 

 most of it, and appears stupid, but does not lose its power of muscular 

 co-ordination. It will not take food, but if food be placed in its mouth 

 it will swallow it, and digestion and excretion will go on as in the un- 

 mutilated animal. It will sit or stand for a long time in one position, 

 will scratch itself and prune its feathers, if thrown into the air it will 

 fly, if pushed it will walk. It appears, moreover, to be influenced 

 through the optic lobes, for if placed in a room partly lighted, it will 

 move to the best illuminated part of it, and will pass to one side of ob- 

 stacles lying in its way. A case is mentioned in which a pigeon, de- 

 prived of its cerebrum, was affected by the light sufficiently to cause the 

 contraction of the pupils when exposed to it suddenly, after confine- 

 ment of the bird for a time in a dark place. And when a lighted can- 

 dle was moved before the eyes of the bird, the head followed the light 

 by a corresponding movement. A vertiginous movement may be in- 

 duced in pigeons by simply blinding one eye. ( Carpenter. ) 



Dr. Ferrier's experiments on the cerebellum prove that it has a con- 

 trol ( though certainly not an exclusive one ) of the ganglionic centers 

 of the < ' motor nerves of the eye, every kind of movement of the eye- 

 balls, even rotation on their antero-posterior axes, being capable of ex- 



