Langdon, The Arachnoid of the Brain. 



209 



which to the edges of the openings produces a multiple 

 crescentic appearance of their margins, which suggests the 

 name adopted above. (See Diagram B.) 



As the body had been subjected to but little handling 

 before the autopsy, and the brain was removed with special 

 care, it does not seem likely that these openings were pro- 

 duced accidentally; the finished appearance of their edges 

 and close correspondence with each other in all respects 

 would also negative this supposition. 



Diagram B. — Lower or ventral surface of pons (P), medulla (M), 

 and cerebellum (C), supposed to be covered by the visceral arachnoid, 

 in which are seen the lunulate foramina (F. L.) in outline. Note. — The 

 artist has failed to represent the membrane, but the outlines of the 

 foramina are correctly placed. 



It is evident that, if constant, they form a large and direct 

 communication between the arachnoid cavity and the sub- 

 arachnoid space and ventricles, just opposite the " foramen 

 of Magendie " — by which the subarachnoid space is stated 

 by most anatomists to communicate with the internal 

 cavities. 



Hence, it would seem reasonable to suppose that the 

 cerebro-spinal fluid may have its origin, in large part at 

 least, in the walls of the arachnoid cavity proper, reaching 

 its final destination through the limulate foramina to the sub- 



