20 Journal of Comparative Neurology. 



obtained well-stained preparations of the dura-mater after the 

 injection of a methylen blue solution with a view of staining the 

 nerves of the pia-mater. 



In a number of such preparations the terminations of the 

 dural nerves were well stained and it is to this that I propose 

 to confine my remarks. Alexander (9) made observations with 

 the gold chloride method on the nerves in the dura of the dog, 

 Guinea-pig, rabbit, rat, mouse, dove and frog, and found two 

 kinds of nerves, — vessel-nerves and dural-nerves. He then 

 states that the arteries of the dura, to their microscopic 

 branches are accompanied by two small nerve bundles which 

 run parallel to the vessel. These bundles become smaller toward 

 the periphery until ultimately only single, medullated nerves 

 are found by the side of the vessels. From these medullated 

 fibers, non-meduUated branches are given off which go toward 

 the vessels and terminate thereon ; their mode of ending he 

 could not ascertain. The dural nerves, he states, have their ori- 

 gin directly from the larger nerve bundles or from those follow- 

 ing the vessels. These bundles of medullated nerves, after di- 

 vision, end in non-medullated fibers which form plexuses, often 

 with very narrow meshes. These plexuses seemed in no way 

 connected with the vessels. Whether this was a true plexus or 

 only a network could not be ascertained. Alexander, however, 

 if I read him correctly, inclines to the former view. 



My own observations led me to the conclusion that in the 

 dura mater of the dog, cat and rabbit two kinds of nerves were 

 to be found : 



a. Sympathetic nerves forming peri-vascular plexuses. 



b. Medullated, sensory nerves terminating in the dura. 

 The sympathetic nerves form peri-vascular plexuses, which 



in every respect resemble those already described for the pia- 

 mater and those found about arteries in other parts of the body. 

 They have been found most clearly stained on the middle men- 

 ingeal artery ; this seemed to me, however, accidental, as the 

 portion of the dura containing this vessel and its branches is 

 more easily removed and seemed better stained than other parts 

 of the dura. 



