1 94 Journal of Comparative Neurology and Psychology. 



the nerve cells of Lophius, Holmgren describes an interesting feature 

 of its distribution in the cell. Its ground substance has a two-fold 

 arrangement relative to the centrosome ; in radii which widen as they 

 approach the periphery of the cell, and in concentric circles around 

 the centrosome. Both the radial and circular bands are more or less 

 irregular in outline. This typical arrangement, however, is often 

 found modified or obscured. The circular bands may overlap each 

 other and those which come nearest the nucleus are more or less di- 

 verted from their symmetrical course so as to encircle the nucleus. 

 And on the side of the nucleus nearest the centrosome the tigroid 

 substance collects into a mass of unusual size and becomes involved 

 in the process of transfusion of nuclear substance into the cytoplasm 

 as we have described in the section relating to the nucleus. 



Holmgren ('do) believes that the distribution of the tigroid bodies 

 is determined by the arrangement of the canaliculi. He has noticed 

 that the tigroid substance of a given cell is most abundant in the 

 region of the most conspicuous canaliculi ; also, that it is very abun- 

 dant in the nerve cells of animals which are characterized by numer- 

 ous canaliculi. Furthermore, electrical stimulation of the nerve cell 

 is accompanied by an increase in the tigroid substance and also by an 

 expansion of the canaliculi. 



Although Holmgren's interpretation regarding the increase in 

 tigroid substance under electrical stimulation of the nerve is open to 

 serious objection, his observation would nevertheless support his thesis 

 that the condition of the tigroid substance is correlated with that of 

 the canaliculi. This idea received further support from the observa- 

 tions of PuGNAT ('oi) who finds that the canaliculi appear synchro- 

 nously with the tigroid bodies in the embryonic nerve cell of the chick. 



Regarding the function of the tigroid substance, its relation to 

 the ground substance and its embryogenesis point to the same conclu- 

 sion : that it is a nucleoproteid whose kinetic energy is transformed 

 into potential energy by the metabolism of the cell. The distribution 

 of the substance through the cytoplasm may, as Scott points out, 

 contribute to a more prompt and rapid metabolism than if the activ- 

 ities were restricted to the nucleoproteids within the nucleus. This 

 interpretation seems to be born out further by the facts of chroma- 

 tolysis. 



//. Chromatolysis. — In the strict sense "chromatolysis" applies 

 only to a progressive diminution of the chromatic substance of the 

 cell, but other phenomena which seem to be concomitant with this 

 change will be, for convenience, included in this discussion. 



