274 SEKOUS MEMBRANES, BY E. KLEIN. 



The bloodvessels of the dura mater consist, according to 

 Recklinghausen (21), and Bohm (22), of a venous plexus situated 

 on the external surface, the branches of which are dispropor- 

 tionately large. In the Dog in particular the venous branches 

 coalesce to form large sinus-like spaces between the arteries. 

 Bohm has observed these venous plexuses become filled from 

 the inner surface of the dura mater, and is therefore of opinion 

 that a free communication exists between the veins of the ex- 

 ternal surface of the dura mater and those of the serous cavity 

 of the cranium. 



The bloodvessels may be followed and studied, even in their 

 finest ramifications, by means of injections, and in specimens 

 prepared with silver and gold ; the latter mode of preparation 

 in some instances permits injections to be entirely dispensed 

 with. 



E. NERVES. 



The nerves supplying serous membranes have received but 

 little attention. According to Cyon (23), the nerves distributed 

 to the septum between the peritoneal cavity and the cysterna 

 lymphatica magna of the Frog are doubly contoured, and run 

 in small fasciculi of two or three enclosed in a separate sheath. 

 After undergoing subdivision to a greater or less extent, they 

 lose their medulla, and form fibres that bulge at intervals from 

 the presence of nuclei. 



At those points where a fasciculus breaks up, broad nucleated 

 fibres appear, that possess a distinctly fibrillated structure. 



The several fibres, by their crossing and mutual entwining, 

 form a plexus with rhombic meshes of various size. Cyon 

 considers that this plexus is not 'terminal, but that the fibres 

 end in the tissue by free extremities. 



The nerves entering the mesentery are composed of me- 

 dullated fibres, one or two of which accompany the larger 

 bloodvessels. Both the isolated fibres and the fasciculi pursue 

 a well-marked wavy course. 



The few branches given off laterally -as they pass outwards 

 are composed of one or two non-medullated fibres, also charac- 

 terized by the presence of ^projecting nuclei at intervals ; ulti- 

 mately the individual non-medullated fibres form a rhombic- 



