70 



GENERAL ANATOMY. 



a 



FIG. 45. Cell from the anterior horn of the 

 gray matter of the spinal cord, a, Axis-cylinder 

 process. 6. Aggregation of pigment-granules. 

 (From Obersteiner.) 



of cells, commonly called nerve-cells or ganglion-corpuscles, containing nuclei and 

 nucleoli. The cells together with the blood-vessels in the gray nerve-substance, 

 and the nerve-fibres and vessels in the white nerve-substance, are imbedded in a 

 peculiar ground-substance, named by Virchow neuroglia, and consisting of large 

 branched cells (Fig. 46, C), the branches passing in every direction among the 



nerve-tissue, thus holding it and binding it 

 together. It is developed from the epi- 

 blast, and contains neither the character- 

 istic fibres nor cells of connective tissue, 

 and therefore cannot be regarded as be- 

 longing to the true connective tissues. 

 Each nerve-cell consists of a finely gran- 

 ular protoplasmic material, of a reddish or 

 yellowish-brown color, which occasionally 

 presents patches of a deeper tint, caused 

 by the aggregation of pigment-granules 

 (Fig. 45). No distinct limiting membrane 

 or cell-wall has been ascertained to exist. 

 The nucleus is, as a rule, a large, well- 

 defined, round, vesicular body, often pre- 

 senting an intranuclear network, and con- 

 taining a nucleolus which is peculiarly 

 clear and brilliant. The nerve-cells vary 

 in shape and size ; some are small, spher- 

 ical or ovoid, with generally an even out- 

 line, such as those found in the spinal 

 ganglia ; others, again, are caudate or stel- 

 late in shape, and are characterized by their large size and by their having one 

 or more tail-like processes issuing from them, which occasionally divide and sub- 

 divide into numerous branches 

 (Fig. 46, A). These are found 

 in greatest number in the gray 

 matter of the spinal cord. Still 

 others are flask-shaped, as in 

 the cortex of the cerebellum ; or 

 conical, as in the cerebral convo- 

 lutions. For the most part nerve- 

 cells have one or more processes, 

 and they are distinguished by 

 the number of these processes, 

 as unipolar, bipolar, or multi- 

 polar cells. These processes are 

 very delicate and are direct con- 

 tinuations of the protoplasm of 

 the nerve-cell. The majority of 

 the processes of a multipolar cell 

 are exceedingly fine, and branch 

 dendritically, spreading out 

 among the adjacent nervous 

 elements ; these processes are 

 termed the protoplasmic processes 

 or dendrites. One of the pro- 

 cesses, however, does not thus 

 branch, but gives off from time 

 to time lateral branches termed collaterals, and eventually form the axis-cylinder 

 of a nerve-fibre ; this is the axis-cylinder process. 



The white or fibrous nerve-substance or nerve-fibre is found universally in the 



FIG. 46. Cells of nervous system impregnated with silver 

 (Golgi's method). A. Cell from the cortex of the cerebral 

 hemispheres (after van Gehuchten). a. Protoplasmic process. 

 b. Axis-cylinder process, c. Collaterals. B. T-shaped cell 

 from spinal root ganglion (after van Gehuchten). C. Neuroglia- 

 cell from the white substance of the cerebellum (after Kol- 

 liker). 



