CEREBRUM. 187 



From the study of comparative anatomy, pathology, vivisection, etc., evi- 

 dence has been obtained which throws some light upon the physiology of the 

 cerebral hemispheres. 



1. Comparative anatomy shows that there is a general connection between the 

 size of the brain, its texture, the depth and number of convolutions, and the 

 exhibition of mental power. Throughout the entire animal series, the 

 increase in intelligence goes hand in hand with an increase in the develop- 

 ment of the brain. In man there is an enormous increase in size 

 over that of the highest animals, the anthropoids. The most cultivated 

 races of men have the greatest cranial capacity; that of the educated 

 European being about 116 cubic inches, that of the Australian being about 

 60 cubic inches, a difference of 56 cubic inches. Men distinguished for 

 great mental power usually have large and well-developed brains; that of 

 Cuvier weighed 64 ounces; that of Abercrombie, 63 ounces; the average 

 being about 48 to 50 ounces. Not only the size, but, above all, the 

 texture, of the brain must be taken into consideration. 



2. Pathology. Any severe injury or disease disorganizing the hemispheres 

 is at once attended by a disturbance or an entire suspension of mental 

 activity. A blow on the head, producing concussion, or undue pressure 

 from cerebral hemorrhage, destroys consciousness; physical and chemic 

 alterations in the gray matter have been shown to coexist with insanity, 

 and with loss of memory, speech, etc. Congenital defects of organization 

 from imperfect development are usually accompanied by a corresponding 

 deficiency of intellectual power and of the higher instincts. Under these 

 circumstances no great advance in mental development can be possible, and 

 the intelligence remains of a low grade. In congenital idiocy not only is 

 the brain of small size, but it is wanting in proper chemic composition, 

 phosphorus, a characteristic ingredient of the nervous tissue, being largely 

 diminished in amount. 



3. Experimentation upon the lower animals e. g., the removal of the cerebral 

 hemispheres, is attended by results similar to those observed in disease and 

 injury. Removal of the cerebrum in pigeons produces complete abolition 

 of intelligence, and destroys the capability of performing spontaneous 

 movements. The pigeon remains in a condition of profound stupor, 

 which is not accompanied, however, by a loss of sensation or of the power 

 of producing reflex or instinctive movements. The pigeon can be tem- 

 porarily aroused by pinching the feet, loud noises, lights placed before the 

 eyes, etc., but soon relapses into a state of quietude, being unable to remem- 

 ber impressions and connect them with any train of ideas, the faculties 

 of memory, reason, and judgment being completely abolished. 



