gg HOWELL. [Vol. IV 



shows usually, indeed, no structure whatever, but takes a deep 

 uniform tint, as though the chromatin material were evenly 

 diffused throughout (see Fig. 8). The nucleus of this form is 

 generally smaller, both relatively and absolutely, than that of 

 the immature cells ; and the cell protoplasm is more deeply 

 tinged with haemoglobin. It is very common to find these 

 cells with the nucleus either placed eccentrically or partially 

 extruded, while in the immature cells no such appearance is 

 ever seen. As the names I have chosen indicate, I consider 

 these two forms the two extremes in the life of the nucleated 

 red corpuscle. Intermediate stages between the extremes are, 

 of course, of frequent occurrence ; for instance, corpuscles with 

 a nucleus which stains deeply and nearly uniformly, but shows 

 large or small irregular clumps of a deeper staining material, 

 like the granules of the nucleus in the younger forms, or others 

 in which the nucleus contains smaller granules staining deeply 

 and some indication of a reticulum between the granules ; while 

 the material between the granules and reticulum, the nuclear 

 liquid, also takes the stain to a certain extent. The morpho- 

 logical difference between the two extreme types of nucleus is 

 associated with a difference in chemical structure, as far as this 

 can be determined by staining reagents. When sections of the 

 marrow are treated with the triple stain, — hasmatoxylin, eosin, 

 saffranin, — the nucleus of the immature forms takes the hsfema- 

 to.xylin, while that of the mature forms stains a brilliant red 

 with the saffranin ; and the nucleus of the intermediate stages 

 shows a combination tint of some shade of purple (see Fig. 9). 

 The distinctness with which this difference in staining comes 

 out depends, of course, upon the time of exposure to the differ- 

 ent dyes. If the section has lain too long in the haematoxylin, 

 all the nuclei of the preparation may be stained a dark blue or 

 purple ; while, if the exposure to the haematoxylin has been too 

 short, the saffranin color predominates to the exclusion of the 

 others. In some degree, however, the difference between the 

 nuclei may be discovered in all cases ; and when the staining 

 has been properly regulated, it comes out with great distinct- 

 ness. The time for the action of each dye varies naturally 

 with the thickness or character of the sections ; but usually a 

 minute to a minute and a half was found to be the proper time 

 of immersion in each of the staining reagents. It is worthy of 



