8 Journal of Comparative Neurology. 



ing respectively, each of the arterial branches. In the prepara- 

 tion from which Figure i was drawn, at the place of division 

 of the nerve bundle into branches a and b, a number of dividing 

 medullated nerves may be observed in which one branch passes 

 to the middle cerebral, the other to the posterior communicat- 

 ing. Similar observations I have repeatedly made. Attention is 

 drawn to this fact to show over how large an area a single med- 

 ullated fiber (sensory fiber) may be distributed, and to show 

 how futile it would be to attempt to localize pain in the pia-ma- 

 ter ; for it must be understood that such diverging branches may 

 now and then be traced in the pia-mater of the cat, for distances 

 approaching an inch, without reaching their termination. 



In preparations of the pia-mater, coming from the base of 

 the brain and embracing the circle of Willis and the anterior 

 and middle cerebrals and their main branches, the medullated 

 nerve fibers, above described as found in connection with the 

 arteries of the circle of Willis, may be traced in connection 

 with the branches of the anterior and middle cerebral to the 

 borders of the preparation. In preparation of the pia-mater 

 from the lateral aspect of the hemispheres they are again found 

 with the vessels and in suitable preparations may be traced to 

 the longitudinal fissures. On the lateral surfaces of the cerebral 

 hemispheres the medullated fibers accompanying the pial vessels 

 appear as single fibers or small bundles consisting of two, three, 

 four or five medullated fibers. The bundles of medullated nerve 

 fibers, as also single fibers, accompanying the pial vessels un- 

 dergo, as before said, repeated division, not only at points 

 of division of the arterial branches but at other points along 

 the course of the vessels. The branches of bundles of medul- 

 lated fibers or single fibers wind around the vessels in long 

 sweeps, and here and there exchange fibers, and in this way 

 form plexuses of large irregular meshes, which surrounds the 

 vessels. 



I have in a number of experiments been able to obtain 

 methylen blue preparations which show most clearly the mode 

 of termination of the medullated nerve fibers under discussion. 

 The most successful preparations come from the cat, through a 



