84 TISSUES OF THE NERVOUS SYSTEM. 



use of the needle can also obtain good preparations by teasing 

 from fresh spinal cords, in iodized serum. In preparations of 

 this kind, in addition to the multipolar ganglion cells, medul- 

 lated nerve fibres, of various diameters, possessed of irregular 

 or regular dilatations (varicosities), and axis-cylinders of va- 

 rious size with distinct fibrillar streaking, are to be met with. 

 In teasing spinal-cord preparations, it is always well to place 

 the glass on a black ground. 



The ganglion cells of the anterior horns of the spinal cord 

 of the calf are remarkable for their size, and consist of a 

 granular cell substance, in which (as may be seen in prepara- 

 tions in iodized serum under very high powers) fibrils may be 

 distinguished. The large round vesicular nucleus which each 

 cell contains, has a double contour, and incloses a highly 

 refractive nucleolus : in its neighborhood there is usually a 

 mass of pigment. Each cell possesses processes of two kinds 

 the so-called axis-cylinder process, and the branched processes. 

 The axis-cylinder process springs from a broad base, from 

 which it tapers to a fine filament. To whatever distance this 

 filament is traced, it is seen that it it does not branch, but 

 becomes thicker, and eventually assumes the character of a 

 medullated nerve fibre. The other processes are broad and 

 flattened, and soon divide dentriticalty. The} 7 consist of fibrils 

 embedded in a coarsely granular interstitial substance: the 

 fibrils can be followed distinctly into the ganglion cell. As 

 we shall see subsequently, the terminations of these processes 

 form a dense network of extremely minute filaments, which 

 network is in equally direct continuity with the endings of 

 the nerve fibres which enter the cord by the posterior roots. 

 The cells of the posterior horns are entirely similar, but some- 

 what smaller. If thin sections of the spinal cord of the pike 

 are hardened in bichromate of potash or chromic acid, washed 

 in water for twenty-four to forty-eight hours, and then placed 

 in diluted ammoniacal solution of carmine for a few hours or 

 a day, good permanent preparations can be obtained by teasing, 

 which can be mounted in glycerin. In the nuclei of Stilling, 

 in the intra-cranial part of the cord, cells occur resembling 

 those of the anterior horn of the spinal cord, and may be pre- 

 pared in the same way. 



Gerlach's method of demonstrating the relation 

 between the ganglion cells and the network of non- 

 medullated nerve fibres in the spinal cord. Longi- 

 tudinal sections, which must be as thin as possible, are made 

 through the anterior horns of the gray substance of a per- 

 fectly fresh spinal cord of the calf or ox ; these are transferred 

 as they are cut into very dilute solution of bichromate of 

 potash (one part in 5,000-10,000), and allowed to remain for' 

 two or three days in a cool place. Thereupon they are placed 



