THE NERVOUS SYSTEM OF MAN. 



41 



of this part. It is therefore the part most immediately 

 necessary to life. The gray matter of the medulla is 

 the center controlling automatically the most vital pro- 

 cesses of the body. Removal of this produces immedi- 

 ate death. 



Optic Lobe.— This is probably the immediate con- 

 troller of the sense of sight; its destruction, therefore, 

 destroys that sense. The optic nerve, coming from the 

 eye, sends one root to the optic lobes and another to the 

 thalamus. The latter sends an influence to the visual area 

 of the cerebrum. We will explain this more fully later. 



Thalamus and Corpus Striatum. — These ganglia are 

 undoubtedly very important and very necessary to life. 

 Their function is still ob- 

 scure, but from their con- 

 nection with the cerebrum 

 on the one hand, and the 

 rest of the body on the 

 other, they seem to be an 

 intermediarybetween these 

 two. Sense impressions 

 from surfaces and sense 

 organs, on their way to the 

 cerebrum, seem to pass 

 through the thalamus and 

 receive impulse from that 

 organ ; and impulses or 

 mandates from the cere- 

 brum on their way outward 

 to the muscles seem to pass 

 through the corpus stria- 

 tum and receive fresh impulse there. They are relay 

 batteries in the course of communication between brain 

 and body (Fig. 27). They are, moreover and especially, 

 centers of semiautomatic or habitual movements. There are 



Fig. 27. — Diagram showing supposed 

 function of thalamus and corpus 

 striatum in relation to the cere- 

 brum : cs, cerebral sensory ; cm, 

 motor ; csm, corpus striatum ; ths, 

 sensory thalamus. 



