GENERAL USES OF THE CEREBRUM. 617 



osition, regarding the intelligence of man as simply superior in degree to 

 that of the lower animals, it is evident that this difference in the degree of 

 development is so great as to render the human mind hardly comparable 

 with the intellectual attributes of animals low in the scale. Still, there can 

 be no doubt with regard to the identity of the nature of the faculties of the 

 brain in man and in some of the lower animals, however much these facul- 

 ties may differ in their degree of development. If this proposition be true, 

 it is reasonable to apply experiments on the brain in the lower animals to the 

 physiology of corresponding parts in the human subject. 



Extirpation of the Cerebrum. Experiments upon different classes of 

 animals show clearly that the brain is less important, as regards the ordinary 

 manifestations of animal life, in proportion as its relative development is 

 smaller. For example, if the cerebral hemispheres be removed from fishes 

 or reptiles, the movements which are called voluntary may be but little 

 affected ; while if the same mutilation be performed in birds or some of the 

 mammalia, the diminished power of voluntary motion is much more marked. 

 It would be plainly unphilosophical 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 js not destroyed by the operation. It is not only possible 

 but probable that in the very lowest of the vertebrates, the operations of the 

 nervous centres are not the same as in higher animals. There is, for exam- 

 ple, a fish (the lancet-fish, Amphioxus lanceolatus), that has no brain, all of 

 the functions of animal life being regulated by the gray substance of the 

 spinal cord. It is essential, therefore, in endeavoring to apply the results of 

 experiments upon the brain in the lower animals to human physiology, to 

 isolate, as far as possible, the distinct manifestations of intelligence from 

 automatic movements. 



Flourens (1822 and 1823) made a series of important observations upon 

 the different parts of the encephalon. As regards the cerebral hemispheres, 

 he found that the complete removal of these parts in living animals (frogs, 

 pigeons, fowls, mice, moles, cats and dogs), was invariably followed by 

 stupor, apparent loss of intelligence and absence of even the ordinary in- 

 stinctive acts. Animals thus mutilated retained general sensibility and the 

 power of voluntary movements, but were thought to be deprived of the spe- 

 cial senses of sight, hearing, smell and taste. As regards general sensibility 

 and voluntary movements, Flourens was of the opinion that animals de- 

 prived of their cerebral lobes possessed sensation, but had lost the power of 

 perception, and that they could execute voluntary movements when an 

 irritation was applied to any part, but had lost the power of making such 

 movements in obedience to an effort of the will. One of the most remark- 

 able phenomena observed was entire loss of memory and of the power of 

 connecting ideas. The voluntary muscular system was enfeebled but not 

 paralyzed. Removal of one hemisphere produced, in the higher classes of 

 animals experimented upon, enfeeblement of the muscles upon the opposite 

 side, but the intellectual faculties were in part or entirely retained. 



