174 SPINAL GANGLIA. [BOOK i. 



on as a nerve fibre. The substance of the cell body is of 

 the kind which we call finely granular protoplasm; sometimes 

 there is an appearance of fibrillation, the fibrillae passing in various 

 directions in the body of the cell and being gathered together in a 

 longitudinal direction in the stalk. Sometimes the cell body 

 immediately around the nucleus appears of a different grain from 

 that nearer the stalk, and not unfrequently near the nucleus is an 

 aggregation of discrete pigment granules imbedded in the proto- 

 plasm. 



The nucleus, like the nuclei of nearly all nerve cells, is large 

 and conspicuous, and when in a normal condition is remarkably 

 clear and refractive, though it appears to consist like other nuclei 

 of a nuclear membrane and network and nuclear interstitial ma- 

 terial. Even more conspicuous perhaps is a very large spherical 

 highly refractive nucleolus ; occasionally more than one nucleolus 

 is present. 



Surrounding the cell body is a distinct sheath or capsule con- 

 sisting of a transparent, hyaline, or faintly fibrillated membrane, 

 lined on the inside by one layer or by two layers of flat, polygonal, 

 nucleated epithelioid cells or plates ; that is to say, cells which 

 resemble epithelium cells, but differ not only in being extremely 

 flattened, but also in the cell body being transformed from 

 ordinary granular protoplasm into a more transparent differen- 

 tiated material. In stained specimens the nuclei of these plates 

 are very conspicuous. Under normal conditions this sheath is 

 in close contact with the whole body of the cell, but in hardened 

 and prepared specimens the cell body is sometimes seen shrunk 

 away from the sheath, leaving a space between them. Occasionally 

 the cell body while remaining attached to the sheath at- three 

 or four or more points is retracted elsewhere, and accordingly 

 assumes a more or less stellate form ; but this artificial condition 

 must not be confounded with the natural branched form which as 

 we shall see other kinds of nerve cells possess. 



When a section is made through a hardened ganglion the plane 

 of the section passes through the stalks of few only of the cells, 

 and that rarely for any great distance along the stalk, since in the 

 case of many of the cells the stalk is more or less curved and conse- 

 quently runs out of the plane of section ; but in properly isolated 

 cells we can see that in many cases, and we have reasons to believe 

 that in all cases, the stalk of the cell is as we have said continued 

 on into a nerve fibre. As the cell body narrows into the stalk 

 several nuclei make their appearance, lodged on it ; these are small 

 granular nuclei, wholly unlike the nucleus of the cell body itself, 

 and more like, though not quite like, the nuclei of the neurilemma 

 of a nerve. They are probably of the same nature as the latter ; 

 and indeed as we trace the narrowing stalk downwards a fine 

 delicate sheath which, if present, is at least not obvious over the 

 cell body, makes its appearance, and a little farther on between this 



