724 FUNCTIONS OF THE CEREBRUM [CH. L. 



phenomena they exhibit are similar to those shown by a frog or 

 pigeon. The difficulty of the operation was overcome by Goltz of 

 Strassburg, in dogs, by removing the cerebrum piecemeal. One dog 

 treated in this way lived in good health for eighteen months, when it 

 was killed in order that a thorough examination of the brain might 

 be made. It was then found that not only the hemispheres but the 

 main parts of the optic thalamus and corpus striatum had been 

 removed also. Though it could still carry out coordinated move- 

 ments, its reactions were entirely reflex, and memory, emotions, 

 feelings, or the capacity to learn were absent. 



The higher animal loses just those characters which distinguish 

 it from the lower ones. It is difficult to prophesy what would 

 happen if as extensive operations were carried out in a monkey or a 

 man. But so far as extirpation has been observed, the initial paralysis 

 (which is seen also in the dog) does not disappear so rapidly or so 

 completely. In man, the tendency to recover is least. 



If we now compare these effects, it is seen that the results of the 

 operation becomes progressively greater as we ascend the scale. The 

 higher the animal, the more fatal the effects, the immediate disturb- 

 ance more severe, the return of function slower, and the permanent 

 loss greater. The long life of G-oltz's dog was doubtless due to the 

 fact that the removal was accomplished by several operations. 



This is anatomically explicable when we remember that the 

 anterior horn cells are influenced chiefly by two sets of impulses, 

 those which enter the cord by the posterior roots, and those which 

 come down from the cerebrum by the pyramidal tracts. In the lower 

 animals the pyramidal pathway is insignificant, and when it is inter- 

 rupted the disturbance is consequently slight. In animals below 

 the mammals it is absent, and going up the mammalian scale it 

 becomes more and more important, as the following figures show : 



In the mouse the pyramidal fibres constitute 1'14 per cent, of those in the cord. 

 guinea-pig 3'0 



rabbit 



cat ,, 7'76 ,, ,, 



man 11-87 



We can therefore quite readily understand that in the apes and 

 in man, a damage to the cortex which causes degeneration of these 

 tracts will cut off many impulses to the anterior cornual cells, and 

 produce a greater or less degree of paralysis. 



There are 80,000 fibres in each pyramidal tract of the human cord. They are, 

 moreover, not the only tracts which connect the cerebrum to the spinal cord, and 

 section of these other tracts (see p. 656) may produce quite as marked paralysis. 

 In man, it appears that when the pyramidal tracts are diseased, it is the finer and 

 more delicate movements which are permanently lost (Schafer.). 



