12 Journal of Comparative Neurology. 



muscle cells are readily stained. As previously stated, the 

 medullated nerve fibers found in the pia-mater have been 

 interpreted as sensory in function. My reasons for this 

 assumption are based on their histological appearances, the 

 nature of their endings and their distribution, and may be sum- 

 marized as follows : 



1. These nerves are distinctly medullated, a fact which is 

 readily made out in methylen blue preparations, although as a 

 rule only the neuraxes are stained. In methylen blue prepara- 

 tions the neuraxes of the medullated fibers stain more deeply 

 at the nodes of Ranvier, and at the nodes present an appear- 

 ance which suggests the Fromman's crosses obtained when 

 treating medullated nerves with a silver nitrate solution. In 

 more deeply stained methylen blue preparations the myelin of 

 medullated nerves stains faintly blue and may then be readily 

 recognized. 



2. The medullated nerves in the pia appear, as has been 

 stated, in relatively large bundles, especially in connection with 

 larger vessels at the base of the brain; these bundles branch and 

 anastomose forming plexuses, with wide meshes, which sur- 

 round the vessels. 



3. The neuraxes of these medullated fibers are much 

 larger than the neuraxes of sympathetic neurons or white 

 rami fibers known to me. Accurate measurements have not 

 been made, yet I feel justified in making this comparison, bas- 

 ing my judgment on a somewhat extended experience with the 

 size and appearance of sympathetic and white rami nerves as 

 seen when stained with methylen blue. The possibility of 

 their being cerebro-spinal motor fibers may, I believe, be dis- 

 missed without further comment. 



4. These medullated fibers branch and re-branch and pre- 

 sent the short internodal segments, usually observed when sen- 

 sory nerve fibers approach their termination. 



5. The non-medullated, varicose, terminal branches of 

 the medullated fibers, the majority of them, at least, end in 

 fibrous tissue — adventitia of vessels or in pia. These terminal 

 fibrils are in the main parallel to the vessels or cross them 



