350 Sheath Cells and Axoiie Sheaths in the Central Xervous System 



general to type A of Fig. 8. Here a continued coalescence of the 

 spaces has resulted in some so large that they more or less completely 

 encircle the axone and are hounded by necessarily condensed portions 

 of the reticulated framework which, at the periphery of the sheath 

 and about the axone, amount to little more than the outer and inner 

 layers of Hatai. The partitions between adjacent large spaces them- 

 selves often contain numerous smaller spaces. These larger spaces 

 encircling the axone may be often so shaped and arranged that in 

 longitudinal section, either optically or by the microtome, the result- 

 ing partitions of the framework between them may easily appear in 

 the more or less conical form. In the left-hand end of the bit of fiber 

 indicated by A, the cones are less apparent than further to the right. 

 Many of the fibers with numerous larger spaces do not show the conical 

 arrangement of the framework, even as distinctly as is indicated in .^4. 



The spaces are interpreted as occupied by globules of myelin, the 

 larger resulting from a coalescence or fusion of the smaller globules. In 

 the normal fresh condition the myelin is probably not in the form of 

 globules at all but as a more finely divided emulsion evenly distributed 

 throughout the framework supporting it. Globulation, beginning as very 

 small globules which later coalesce into the larger, apparently results in a 

 distortion of the natural arrangement of the framework of the myelin 

 sheath. The beginnings of such may be noted even in B of Fig. 8 and in 

 all fibers of its type. In accordance with this view the conical arrange- 

 ment of the framework and all the intermediate forms may be looked upon 

 as artifacts. The material of my preparations was taken at the slaughter 

 house shortly after death and immediately placed into the fixing fluid. 

 That the peripheral nerves were more exposed to the atmosphere and to 

 handling probably explains why globulation is so marked in their fibers 

 and not in those of the spinal cord. However, the material of my Brenda 

 preparations of the human cord was taken 48 hours after death and in this 

 also the sheaths of the central fibers do not show the conical arrangement 

 of the framework. But it also was placed into the fixing fluid immedi- 

 ately upon removal from the body. 



That the medullated sheaths of the peripheral nerve fillers after fixation 

 in weak solutions of osmic acid or after poor osmic fixation usually 

 present the appearance of a coarse network, is a matter of frequent obser- 

 vation. Lantermann himself noted such an appearance. Ewald and 

 Kiihne named it neurol'eratin. The appearance is consider(3d due to 

 the myelin being in the form of imperfectly blackened globules, the 

 interstices between the globules giving a merely optical impression of 

 a network. Pertik, however, interpreted it as indicating the presence 



