EXTIRPATION OF THE CEREBRUM. 329 



in nature as well as in amount. Although we are by no 

 means prepared to accept this proposition, regarding, as we 

 must, the intelligence of man as simply superior in develop- 

 ment to that of the lower animals, it is evident that this 

 difference in the degree of development is so enormous as to 

 render the human mind hardly comparable with the intellect- 

 ual attributes of animals low in the scale. But when the 

 human brain is slightly developed, as in idiots, or when 

 the intellectual faculties are simply diminished in activity, 

 as in certain cases of disease, the being is reduced to a condi- 

 tion very like that of some of the lower animals. 



Experiments upon different classes of animals show clear- 

 ly that the brain is less important, as regards the ordinary 

 manifestations of animal life, in proportion as its relative de- 

 velopment is smaller. For example : if we remove the cere- 

 bral hemispheres in fishes or reptiles, the movements which 

 we call voluntary may be but little affected ; while, if the 

 same mutilation be performed in birds or some of the mam- 

 malia, the diminished power of voluntary motion is much 

 more marked. It would be plainly unphilosophic to assume, 

 because a fish or a frog will swim in water and execute 

 movements after removal of the hemispheres, very like 

 those of the uninjured animal, that the feeble intelligence 

 possessed by these animals is not destroyed by the opera- 

 tion. It is not only possible, but probable, that in the very 

 lowest of the vertebrates, the functions of the nervous cen- 

 tres are not the same as in higher animals. There is, for 

 example, a fish (the lancet-fish, Amphioxm lanceolatus\ that 

 has no brain, all of the functions of animal life being regu- 

 lated by the gray substance of the spinal cord. 1 It is essen- 

 tial, in endeavoring to apply the results of experiments upon 

 the brain in the lower animals to human physiology, to iso- 

 late, as far as possible, the distinct manifestations of intelli- 



1 MEYXERT, in STRICKER, Handbuch der Lehre von den Geweben, Leipzig, 1868, 

 S. 695 ; and, VAN DEB HOEYEN, Handbook of Zoology, Cambridge, 1858, voL il, 

 p. 56. 



