268 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



animal was excessively active, and became more and more excited when 

 ready to defecate or when hungry. 



The examination of the brain showed that in front of the mid-brain the 

 important structures had been removed or were degenerated, only small por- 

 tions of the corpora striata remained, mainly parts of the caudal portions 

 of the nucleus caudatus. The frontal portion of the thalamus had been re- 

 moved and the nuclei in the remainder were highly atrophic, so that the 

 defects were due to a removal of rather more than the cerebrum proper. 



Emotions, feelings, conscious sensations, or the capacity to learn were 

 entirely wanting in this dog, and its reactions were those of a very elaborate 

 machine. 



If we compare, now, the effects of the removal of the cerebral hemispheres 

 in the bony fish, the pigeon, and the dog, we see that the results of the 

 operation are progressively more disturbing as we pass up the series. In 

 the higher animals the effects are more often fatal, the disturbance imme- 

 diately following is much more severe, the return of function slower, and the 

 permanent loss greater. As a partial exception to the above statements is 

 the observation that after operation the general health of pigeons always 

 declines, and it is not possible to keep them alive more than about six weeks. 

 On the contrary, a dog could be kept in good health for some eighteen 

 months; but there is this difference between the experiments, that the 

 removal in the case of the dog was made by several successive operations. 



By removal of the cerebrum the higher animal tends to lose just those 

 capacities which best serve to distinguish it from the lower forms. When, 

 therefore, the inquiry is made why the results obtained in the dog are not 

 obtainable in the monkey or in man, there are several replies. In the first 

 place, no such extensive experiments have been made on monkeys of the 

 right age and under equally favorable conditions. If the mature animal is 

 taken, the secondary degenerations are so massive that they certainly cause 

 great disturbance in the remaining part of the system. This is not equivalent 

 to an assertion that the same results could be obtained in the monkey by more 

 extensive experiments, but :i suggestion of one difference behind the results 

 thus far reported. There is no reason for assuming any deep-seated differ- 

 ence in the arrangement of the central system of the highest mammals as 

 compared with that in the lower. Indeed, in some human microcephalic 

 idiots the proportion of sound and functional tissue in the eneephalon is less 

 than one-lburth that found in a normal person ; yet, on the other hand, no 

 normal adult could lose anything like the amount of tissue which is out of 

 function in these microcephalic brains and at the same time live. 



The central system, therefore, even in man, is to be looked upon as pos- 

 sessed of some power to adapt itself when portions have been lost, but this 

 is most evident when the defect begins early and develops slowly. 



Keeping the cerebrum -till in view, it is possible to go into further 

 details. In tonus below the monkey the loss of portions of the cerebral 

 cortex from tin; motor area is accompanied by a greater or less paralysis of 



