Strong, Nerve Fiber and Cell Body. 399 



enhance the tendency of the cell bodies, dendrites, and also of the 

 axis cylinders to remain stained, with the result that in some cases 

 the cell bodies, coarse dendritic branches and axis cylinder pro^ 

 cesses were stained black, the sheath being stained bluish-black. 

 Often many of the cell bodies were more or less completely decol- 

 orized, but in many of these the "axone cone" and the rest of the 

 axis cylinder process retained the stain. Many preparations were 

 filled with small brown granules between cells and iibers which 

 marred their clearness but did not prevent the cells and their 

 processes from being quite easily observed; in other preparations 

 these granules were practically absent. 



The sections stained with Delafield's haematoxylin presented 

 a somewhat different picture. Here the granules were completely 

 absent and both sheath and axis cylinder were stained blue. The 

 axis cylinders in the white matter were usually more deeply stained 

 than the sheaths. In the cell bodies a considerable variety of pic- 

 tures was displayed. Often the bodies of NissL were very clearly 

 defined; in others, the whole body and dendrites were stained 

 a diffuse deep blue with at times a slightly fibrillar appearance. 

 The cells showing only the Nissl bodies stained did not usually, 

 naturally, exhibit the axis cylinder process. 



The "axone cone" emerging from the cell body or from a 

 dendrite (Fig. 3), usually either tapers regularly to the narrow 

 portion (neck) of the axis cylinder process (Figs. 3 and 5), or first 

 diminishes gradually and then more abruptly (Figs, i and 2). The 

 curves described are so similar to those produced by pulling apart 

 some plastic substance as to suggest that a tension upon this, pre- 

 sumably the weakest, part of the axis cylinder may have been a 

 factor in its production either during growth or as an artefact in 

 fixation, or both. 



The diminution of the axone in diameter at a point near the 

 cell body has long been figured (for example, see Gerlach's figure 

 of an isolated cell, copied in many text-books). In the present 

 preparations it is very strikingly shown. In some, this portion is 

 still thinner than indicated in the accompanying figures. Often, 

 too, the cone and the medullated part of the fiber only are shown, 

 this intervening portion not being visible. This is probably 

 usually due to its being decolorized. This extreme attenuation is 

 not improbably an artefact. The cell bodies in these prepara- 

 tions are often not perfectly fixed and exhibit considerable shrink- 



