304 Journal of Comparative Neurology and Psychology. 



those of the adult, in being more columnar inshape^less easily stained, 

 and in having the nuclei located nearer the cell apex. Soon after 

 birth the cells rather rapidly assume the adult form. In the rat this 

 is accomplished by the seventh day. 



Only recently has definite proof been offered that the plexuses 

 are concerned in the secretion of the cerebro-spinal fluid. This 

 proof rests on the following facts : 



The administration of ether, pilocarpin or muscarin, increases 

 the flow of the fluid. J tropin or hyoscyamin retards the flow. 

 After the administration of muscarin or ether, if the plexuses be 

 removed, the epithelial cells will be found very much modified. 



The apical portion has increased in height, and become clear, 

 zuhile the basal portion has remained granular. In other words, 

 they show changes characteristic of typical secreting cells. The 

 fact that the flow of cerebro-spinal fluid is increased by injection 

 of drugs that usually stimulate secretion in the epithelial cells, 

 and that the cells themselves show secretory changes, justifies the 

 conclusion that the fluid is secreted by the choroid plexuses. The 

 ependymal cells may have their part in the production of the cere- 

 bro-spinal fluid, but it is certainly a minor one compared to that 

 of the choroid plexuses. 



Additional evidence that strengthens this conclusion is the occur- 

 rence of hypertrophy of the plexuses in certain cases of hydro- 

 cephalus. The fact that the fluid differs from the serum or lymph 

 is also in favor of the view that it is a secretion. 



BIBLIOGRAPHY. 



Benedikt. 



'73. Ueber die Innervation des Plexus choroideus inferior. Canstatfs Archives. 

 Cappelleti, E. 



'01. L'ecoulement du liquide cerebrospinal par la fistule cephalorachidienne en conditions 

 normales et sous I'influence de quelques medicaments. Archiv. Ital. de Biol., Vol. 36, 

 pp. 299-302. 

 Cavazzani, a. 



'93. Sur la circulation du liquide cerebro-spinal. Archiv. Ital. de Biol., Vol. 18, p. 475. 

 Cavazzani, E. 



'99. Die Cerebrospinalfistel. Centralblatt fur Physiologie,\o\. 13, p. 345. 

 Catola, G. 



02. Sulla presenza di neuroglia nella struttura du plessi coroidei. Riv. di Patol. Nerv. e 

 Merit., No. 9. 

 Charpy. 



'01. Traite d'anatomie de Poirier et Charpy. t. iii, p. 147. 



