NERVE TISSUE. 



1 97 



Diagnostic weight has subsequently been laid on the finest 

 varicosities of these primitive fibrillar (M. Schultze). 



We shall subsequently return to this. 



We are now, so far as it is at present 

 possible, familiar with the fibres. Let us 

 turn to the cellular elements. They belong 

 solely to the gray substance of the nervous 

 system (the peripheral, as well as the cen- 

 tral) ; the white substance consists through- 

 out solely of nerve tubes. 





SI 





: . 



; 



; 

  





Fig. 173. — Fibrillated 

 arrangement of the 

 axis cylinder ; a, a 

 thick axis cylinder from 

 the spinal cord of the 

 ox ; b, nerve fibre from 

 the brain of the torpedo. 



Fig. 174. — Ganglion cells of the mamma- 

 lia ; a, cells with connective-tissue envelopes, 

 which are continued in fibres, d, d ; a, a cell 

 without a nucleus ; b, two single nucleated 

 ones ; and c, one with two nuclei ; b, a gan- 

 glion body without an envelope. 



We frequently encounter, in a very characteristic form, 

 those cellular elements, the ganglion bodies (Fig. 174, B). It 

 is one of the handsomest cell-forms which the organism pos- 

 sesses. The dimensions of most of the globular, ovoid or 

 pear-shaped elements lies between 0.0992 to 0.0451 and 

 0.0226 mm. In a very delicate granular, thickly gelatinous, 

 generally colorless, occasionally brown or black pigmented 

 mass, we meet with a globular, delicate walled nuclear vesicle, 

 0.0180 to 0.009 mm - in diameter. In it occurs, as a rule 

 single, a dull glistening granule, the nucleolus, 0.0029 to 

 0.0045 mm - m si ze - 



