192 Jonnial of Comparative Neurology and PsycJiology. 



onstrating the presence of iron, prolonged treatment will extract all 

 the iron and render the tissue colorless nnder the toluidin blue stain. 

 Yet after all the iron has been extracted phosphorus is still demon- 

 strable in the tigroid substance and in the oxyphile and basophile nu- 

 clear substance. Treatment with alkalies removes the iron from the 

 tigroid substance but not from the nucleolus and the oxyphile nuclear 

 substance, excepting when the treatment is prolonged, while the nu- 

 clei of neuroglia cells in the same preparations stain normally in eosin 

 and toluidin blue. Prolonged treatment in the alkalies, however, 

 does not affect the phosphorus of the cell. The author finds that 

 fresh defibrinated ox-blood, owing to its alkalinity, has the same effect 

 as potash of soda upon the nerve cells fixed in alcohol. 



By these differential methods Scott concludes that the tigroid 

 substance is one oi at least three nuclein compounds found in the 

 nerve cell, the other two being the "basophile covering of the nucleo- 

 lus and the oxyphile nuclear substance." The descent of the three 

 compounds was traced by Scott from the chromatin of the germinal 

 cell. "The chromatin," he says, "divides into two parts, each con- 

 taining iron and phosphorus, but the one is oxyphile and remains in 

 the nucleus, while the other is basophile and diffuses into the cell body 

 and becomes the Nissl granules." This position would seem to be 

 supported, also, by van Gehuchten {'97) who is inclined to think 

 that the nuclein (chromatin) of the karyochrome cell is equivalent to 

 the chromatin substance of the somatochrome cell. 



If the nuclear chromatin is the source of the first chromatic ele- 

 ments in the cytoplasm of the embryonic nerve cell, does it continue 

 this role in the adult cell ? If it does, in what manner is the dis- 

 tribution of the chromatic elements from the nucleus to the cytoplasm 

 brought about ? 



Holmgren ('99) has described an elaborate process, which we 

 have discussed in the section relating to the nucleus, by which the nu- 

 clear wall breaks down and the oxyphile nuclear substance migrates 

 into the cytoplasm and becomes at the same time metamorphosed into 

 basophile tigroid substance. By the same process also the basophile 

 covering of the nucleolus breaks off in large masses which are carried 

 out into the cytoplasm. Scott, however, since he considers that the 

 breaking down of the nuclear membrane and the displacement of the 

 nucleolus is an artifact, is convinced that, if the transference of chro- 

 matic substance from the nucleus to the cytoplasm continues during 

 adult life, the process is diffusion and in no sense a transposition of 

 formed chromatic bodies. However, the nuclear origin of the tigroid 



