CoGHiLL, Structure of the Nerve Cell. 191 



time. Such a hypothesis is supported also by the fact, observed by 

 several investigators, that karyokinetic figures occur in the nerve cells 

 of animals infected with rabies. 



Hatai, however, finds the centrosome present in the nerve cell 

 of the adult rat, though it is not so generally found in the adult as in 

 the young. The centrosphere is here densely surrounded with neuro- 

 somes which go out in radial lines from it, somewhat as Koi.ster finds 

 in Petromyzon . Within the clear centrosphere Hatai finds, also, radii 

 of extremely fine granules centering in the centrosome and staining 

 like it. In some cases the place of the single centrosome may be 

 taken by a number of smaller granules, but in such cases the radial 

 arrangement in the centrosphere is lost. Hatai ('02) describes also 

 the behavior of the centrosome in the mitosis in the embryonic nerve 

 cell. One of the two centrosomes seems to migrate to the opposite 

 pole of the nucleus and then each divides, giving two centrosomes in 

 each centrosphere during the mitotic process. 



The Ti^^roid Substa/icc and Chronatolysis. 



I. Structural and Cheniical Features. — The studies of Scott ('99) 

 upon the chemistry of the tigroid substance of the nerve cell are espe- 

 cially noteworthy since they are based upon both embryological and 

 comparative methods, and since he has employed both cytological and 

 micro-chemical technique. He has not confined himself to the use of 

 the NissL method, but has used toluidin blue and eosin to differentiate 

 the oxyphile and the hasophile substances. 



By the haematoxylin method for the Prussian blue reaction after 

 treatment of the tissue with acid ferrocyanide, and by the ferrous 

 sulphide reaction after treatment with ammonium sulphide and glycer- 

 ine, the basophile and oxyphile nuclear substance and the tigroid 

 bodies show the presence of iron. By the oxide of molybdenum re- 

 action after treatment with a nitric acid solution of ammonium molyb- 

 date followed by phenylhydrazin hydrochloride the same elements of 

 the cell show the presence of phosphorus. In digestive tests Scott 

 finds that immersion for several days in 0.2 per cent hydrochloric 

 acid, at 37 °C., does not affect the oxyphile nuclear substance, but 

 after digestion in pepsin and hydrochloric acid the oxyphile substance 

 cannot be demonstrated by the most vigorous stains. In the pepsin 

 experiments the nucleolus sometimes disappears, but Scott considers 

 that it is only loosened from the slide by the digestion of its oxyphile 

 center by which it may have been attached. 



While treatment of the nerve cell with acid alcohol aids in dem- 



