HISTOLOGY OF THE THYMUS 315 



the granulae gradually assume a dark greenish color, reaching 

 its maximum intensity after eight or ten minutes. The concen- 

 tration of the dye appears to have slight influence upon the rate 

 of staining, but as in the case of the small cells, concentrated 

 solutions produce a reddish staining of the nucleus. The smallest 

 granulae appear to stain first and most intensely, and transitions 

 of every degree are noted up to the large refractile unstained 

 fat drops. The largest droplets often have a pronounced greenish 

 tinge in certain focal planes; whether this is due to refraction of 

 the color from surrounding stained granules, or whether the fat 

 globules are enclosed in a stained shell, could not be decided. 

 "Without entering into a discussion of the role of the cell granulae 

 in the synthesis of fat, it may be said that the appearance noted 

 rather suggests the direct transformation of the granules or a 

 portion of them into fat. Not only are there apparent tran- 

 sitions between the stained granules and the larger refractile 

 droplets, but in Sudan preparations, the fat droplets may be of 

 extremely small size, and distributed in the same linear align- 

 ment as the normal granulae. An attempt was made to examine 

 more closely into the relation of the granules to the fat drops, 

 by fixing the vitally stained cell, and subsequently staining with 

 Sudan III; but it was found that the Janus green was rapidly 

 decolorized by the formalin. 



As the staining with Janus green progresses, there occurs a 

 remarkable contraction of the entire cell. The long plasmatic 

 prolongations are shortened, thickened and gradually withdrawn 

 into the cell body. The entire cell becomes plumper and tends 

 to assume a globular shape, the granulae and fat drops becoming 

 clumped about the nucleus. The phenomenon may occupy only 

 a few minutes. After having taken on a spherical shape, the 

 cell for a time extrudes rounded ectoplasraic pseudopodia in 

 various directions. This takes place even when the nucleus is 

 distinctly stained reddish by the dye, and as has been said, this 

 affords an example of nuclear staining in a cell which though 

 injured, still shows vital activity. 



Gradually these amoeboid extrusions cease, and the cells ]-emain 

 indefinitely in a globular form. The staining, however, fades 



THE AMERICAN JOURNAL OP ANATOMY, VOL. ]4, NO. 3 



