THE NERVOUS SYSTEM. 199 



and a respiratory centre. The glycosuric centre has been already 

 referred to (see Liver}. 



PONS VAROLII. 



The superficial fibres are not excitable or sensible; the deeper 

 are excitable, and the posterior are only sensible. It presides over 

 voluntary motion and sensation. 



CORPORA STRIATA. 



Electrical stimulation of one of these causes general muscular 

 contraction on the opposite side. Destruction of the internal cap- 

 sule causes loss of motion and sensation on the opposite side of 

 the body. The anterior part of the internal capsule is motor, 

 the posterior sensory. 



CORPORA QUADRIGEMINA. 



They are situated in the path of visual conduction, and are con- 

 nected with the sense of sight and the reflex movement of the iris. 



OPTIC THALAMI. 



These are probably connected with sensation, vision and com- 

 plex muscular actions, though their function is not thoroughly 

 understood. 



OLFACTORY LOBES. 



These are the centres for the special sense of smell, and their 

 destruction causes a loss of this, sense. Fibres have been traced 

 to the uncinate gyrus, temporo-sphenoidal region and optic 

 thalami. 



CEREBELLUM. 



The cerebellum presides over the coordination of movements 

 of progression, being connected intimately with the superior col- 

 umn of the cord. Their destruction leads to absence of coordi- 

 nation. 



CEREBRUM. 



The cerebral hemispheres are the centres of intellect or -mind, 

 receiving impressions and giving off impulses. An animal de- 

 prived of the cerebrum retains the special senses of sight, sound, 

 taste, etc., but the intellectual faculties are all lost. From experi- 

 mentation on the lower animals and by observation in disease, 

 centres have been located which preside over certain functions. 



The motor area is located in the cortex above the fissure of 



