202 'Journal of Comparative Neurology and Psychology. 



extent by the walls of the ventricles, and thus reach the true ner- 

 vous tissues. Lewandowsky ('oi) finds that an amount of strych- 

 nine so small that when injected into the blood there is no result, 

 causes violent spasms if injected into the subdural spaces. From 

 this he argues that the fluid bathes the nervous tissue and carries 

 the poison directly to the nerve cells. There can be no doubt that 

 the fluid is in intimate relation to the nervous tissues, nor that 

 small amounts of poison might reach the nerve cells more surely 

 by way of the subdural channels, than by the systemic blood 

 stream, still the fluid can scarcely be distinctively nutritive. It 

 is too poor in proteid. One function that it undoubtedly has is 

 the purely mechanical one of supporting the nervous walls, pre- 

 venting friction, and serving as a water bed for the brain and cord. 

 This is probably its main function. Pettit and Girard ha,ve 

 suggested that it may also serve as some kind of an internal secre- 

 tion, but for this suggestion no evidence has been presented. 



Having been secreted, the cerebro-spinal fluid accumulates in 

 the ventricles and their continuations, and in all the spaces beneath 

 the dura. The connection between the ventricular cavities and 

 the subdural spaces has been thought to be by means of the fora- 

 men of Magendie and the two lateral foramina of the fourth 

 ventricle. According to Milian ('04), some doubt seems to have 

 been thrown on the presence of these foramina by the recent work 

 of Cannieu and Gentes. They consider the above mentioned 

 foramina due to post-mortem changes, and in a number of cases 

 the foramina could not be demonstrated. It is possible, then, 

 that the manner of communication between the ventricles and the 

 subarachnoid spaces is not yet definitely known. Milian ('04) 

 and Cathelin ('03) hold that the fluid reaches the lymphatic 

 system from the subarachnoid spaces by means of the arachnoid 

 sheaths around the nerves, the Pacchionian bodies and the peri- 

 vascular lymphatic sheaths. 



SUMMARY. 



The animals used in this study were the albino rat, guinea pig, 

 cat, dog, sheep and man. The best microscopic preparations were 

 made from material fixed in Bouin's or Carnoy's solution, and 

 then stained in iron hsematoxylin and fuchsin. As a control, 

 examination was made of fresh material either in cerebro-spinal 

 fluid or in physiological salt solution. 



