348 fShcatli (V'lls and Axouu Slicaths in tlie Central Xervous System 



stained by the Bend a method. The root fibers were chosen for the illus- 

 trations because, being on the same slides as the sections of the spinal 

 cord, they were subjected to the identical fixation, treatment and decol- 

 orization as the fibers in the cord, and were therefore deemed better for 

 comparison with the conditions found in the cord. 



The form of sheath framework shown in A, Fig. 8, is no doubt the 

 form to which attention has been usually given in the literature. In 

 this the reticulated framework is more or less condensed into interfitting 

 conical partitions between masses of less intimately supported myelin. 

 In this condensation the outer and inner " membranes " (p and cil) are 

 maintained and rendered even more evident. The partitions when in 

 the form of cones are so arranged that the bases of the cones are con- 

 tinuous with the peripheral membrane and the apices with the axolemma. 

 This is necessarily the case. Otherwise they would not be conical. When 

 a sheath shows the decided conical arrangement for any considerable 

 distance, which it very seldom does, the cones are not necessarily arranged 

 ])arallel and interfitting throughout the distance. For a short extent 

 tliey may be parallel, then irregular cones may be interposed or cones 

 with their apices pointing in opposite directions. The most perfectly 

 formed cones themselves contain openings of the same optical properties 

 as the spaces between the cones. As stained here the cones appear to 

 consist of a fibrillated reticulum with the meshes greatly elongated in 

 the direction occupied by the cone between the axone and the periphe^3^ 

 In A, a fiber was found through which the knife passed obliquely at a 

 region of more or less perfectly formed cones. This allows a certain 

 amount of perspective. Luckily the region also possessed a sheath nu- 

 cleus. It is here especially evident that the cones do not fit cleanly 

 upon the axone but are continuous witli the axolemma both above and 

 below by a more irregularly dispersed portion of the reticulum in such a 

 way as to give an appearan-ce resembling an open umbrella, the rib-braces 

 of which often extend to the apex of the adjacent cone (c. Fig. 8). The 

 appearance shown in the transverse section indicated by A is frequently 

 seen in the sections of peripheral fibers and is interpreted as a section 

 involving the base of one cone and the apex of another. The heavier 

 fibrillse show a peculiar whirled arrangement which is probably due to 

 the lamellae of both cones being cut at levels where they are curving upon 

 the axone in the one case and the periphery in the other. 



Though frec[uently cones are to be found in the hog material somewhat 

 longer than the example chosen in .1^ I have as yet seen none as long as 

 certain of the cones pictured by Hatai and Wynn for the peripheral nerves 

 of the animals thev studied. The finelv fibrillated reticular nature of 



