S9 o TEXT-BOOK OF PHYSIOLOGY 



with the cerebellum of the same but chiefly of the opposite side. The 

 occipito-temporal tract, originating in the cells of the cortex of both the 

 occipital and temporal lobes, passes downward and inward toward the 

 lenticular nucleus, beneath which it passes to enter the outer one-fifth of the 

 crusta. It then enters the pons, and through the nucleus pontis also comes 

 into relation with the cerebellum of both sides. (See Fig. 239, page 575.) 



THE FUNCTIONS OF THE CEREBRUM 



The functions of the cerebrum comprehend, in man at least, all that 

 pertains to sensation, cognition, feeling, and volition. All subjective experi- 

 ences, which in their totality constitute mind, are dependent on and asso- 

 ciated with the anatomic integrity and the physiologic activity of the cere- 

 brum and its related sense-organs, the eye, ear, nose, tongue, etc. 



From an examination of the anatomic development of the brain in different 

 classes of animals, in different men and races of men, and from a study of the 

 pathologic lesions and the results of experimental lesions of the brain, evi- 

 dence has been obtained which reveals in a striking manner the intimate 

 connection of the cerebrum and all phases of mental activity. 



1. Comparative anatomic investigations show that there is a general connec- 



tion between the size of the brain, its texture, the depth and number ot 

 convolutions, and the exhibition of mental power. Throughout the 

 entire animal series an increase in intelligence goes hand in hand with 

 an increase in the development of the brain. In man there is an enor- 

 mous increase in size over that of the highest animals, the anthropoid 

 apes. The most cultivated races of men have the greatest cranial 

 capacity, that of the educated European or American being approxi- 

 mately 92.1 cubic inches (1835 c.c.); while that of the Australian is but 



81.7 cubic inches (1628 c.c.). Men distinguished for great mental 

 power usually have large and well-developed brains; e.g., that of Cuvier 

 weighed 64.4 ounces (1830 grams); that of Abercrombie, 63 ounces 

 (1786 grams). A large intelligence, however, is not incompatible with 

 a much smaller brain weight; thus, the brain of Helmholtz weighed but 



50.8 ounces (1440 grams); that of Leidy, 49.9 ounces (1415 grams); 

 that of Liebig, 47.7 ounces (1352 grams). The average brain 

 weight of 96 distinguished men has been found to be 51.9 ounces 

 (1473 grams) (Spitzka). 



2. Pathologic changes and mechanic injuries which disorganize the cerebrum 



are at once followed by a disturbance or an entire suspension of mental 

 activity. Concussion of the brain or sudden compression from a hem- 

 orrhage destroys consciousness. Physical and chemic alterations of 

 the gray matter of the cerebrum have been shown to coexist with insan- 

 ity, loss of memory, loss of articulate speech, etc. Congenital defects of 

 organization are accompanied by a deficiency in mental capacity and 

 the higher instincts. Under such circumstances no great advance in 

 brain development is possible and the intelligence remains at a low 

 level. In congenital idiocy the brain is small, imperfectly developed, 

 and wanting in proper chemic composition. 



3. Experimental lesions of the brain in lower animals are attended by results 



similar to those observed in disease or after injury in man. Removal 



