34 



The cytoplasm is, as already noted, great as to actual 

 quantity. Some neurones when stained by the metiiod oi' Nissl 

 absorb the methylen-blue equally throughout all parts of the 

 cytoplasm, and hence they appear almost homogeneous; the sig- 

 nificance of this fact is noted below. Other neurones in the 

 same section exhibit a large quantity of tigroid substance; 

 the neurone represented in Fig. 44 is of this type. In the 

 vicinity of the nucleus the ti groid-bodies are usually trian- 

 gular in outline, and some of them have a very considerable 

 size. Tigroids are found far out in the dendrites, assuming 

 here a lenticular or even a linear form, their long axes paral- 

 lel «ith the course of the dendrite. A finely granular axone- 

 hillock lies at the origin oi the axone. In rectangular cells, 

 as the one figured, the hillock ir,ay be spread so widely as to 

 assume a disk-like form. The tigroids tend to become somewhat 

 smaller in the region of the hillock. 



The tract-neurones are not demonstrated readily with either 

 chronie-silver impregnation or the intra-vitum injection of 

 methylen-blue. The homogeneous coloration assumed by some of 

 them with Nissl staining has already been recorded. The charac- 

 ter of such micro-chemical reactions indicates clearly that 

 many of these neurones are not physiologically active, at least 

 not all of the time. The axones from some of theni niay enter 

 the motor root of one of the anterior spinal nerves, and, being 

 in an active condition, give indications of it in a well-marked 

 store of tigroid substance. Other neurones, however, chaining 



