502 



THE NERVOUS SYSTEM. 



Functions of the Cerebral Ganglia. A marked change has taken 

 place within comparatively recent times as to the functions and 

 importance of the corpora striata and the optic thalami. The 

 former were for a long period of time considered important motor 

 centers, and the latter as performing the same role with reference 

 to sensation. This was doubtless largely due to the fact, to which 

 Kirkes calls attention, that when a hemorrhage took place in the 



FIG. 292. Sections of optic lobe of bird 

 taken in planes at right angles to one another 

 (S. Ramon y Cajal) (Golgi method). 



A. Anteroposterior section : a, optic fibers 

 cut across. The other letters indicate differ- 

 ent kinds of cells, of which it will be noticed 

 that some have their axis-cylinder processes 

 extending outward toward the optic fiber 

 layer, and others have their axis-cylinder 

 processes extending inward toward a deep 

 layer of nerve-fibers ; s, some have only short 

 neurons ramifying in adjacent layers. 



B. Transverse section : a, optic fibers cut 

 longitudinally; b, c, d, e, their terminal 

 ramifications in different layers of the gray 

 matter. 



region of the corpora striata, motor 

 paralysis was the result ; and that 

 when it occurred in the region of 

 the optic thalamus, sensory paral- 

 ysis followed. It was, therefore, 

 natural to attribute motion and 



sensation to these ganglia respectively. It is now known that 



?d to these i 



when the hemorrhage is limited to these ganglia paralysis is slight, 

 or even absent altogether, and that the effects of cerebral hemor- 

 rhage ordinarily observed are due to injury of the internal capsule ; 

 and hemorrhage into the anterior portion is followed by motor 

 paralysis, because it is here that the fibers pass which carry 

 motor impulses from the cortex to the cord ; and that hemorrhage 



