No. I.] BLOOD CORPUSCLES. 89 



mention that the nucleoli of the marrow cells and giant cells, 

 as well as the nuclei of cells during karyokinesis, when treated 

 with the triple stain, take the saffranin in preference to the 

 ha:mato.\ylin, like the nuclei of the mature nucleated red corpus- 

 cles ; whereas the reticulum of the resting nucleus of most cells, 

 unlike the nucleolus, stains most easily with the haematoxylin. 

 A similar difference in the behavior of the nucleolus and the 

 dividing nucleus has been noticed before by Steinhaus (48) for 

 epithelial cells, and by Hodge (40) for nerve ganglion cells. 

 With the triple stain of Biondi, the nucleus of the mature 

 nucleated red corpuscles stains an even solid green, and in the 

 nucleus of the immature forms the reticulum and granules at 

 the nodal points stain a light green, while the nuclear material 

 between the meshes of the reticulum remains unstained. 



2. The next most important element of the marrow from 

 our standpoint is a colorless cell, similar in structure to the 

 immature form of nucleated red corpuscle, from which it dif- 

 fers in fact only in the absence of haemoglobin from the cell 

 protoplasm. The nucleus is granular without anything like a 

 definite nucleolus. In well-preserved specimens the granules 

 are connected by an intra-nuclear reticulum, which stains less 

 deepl}^ than the granules. This form of cell has been de- 

 scribed by Osier (28), and also by Lowit (29) and others, as the 

 progenitor of the nucleated red corpuscle. Lowit has given to 

 the cell the name of erythroblast. It seems to me that the 

 name is a convenient one, and I shall make use of it hereafter. 

 At the same time, I wish to say that I do not accept Lowit's 

 theory of the origin and permanent histological characters of 

 these cells, which has been described in the historical review. 

 On the contrary, my investigations have brought me to quite 

 different conclusions, as I shall show in the proper place- 

 Drawings of this form of cell are shown in Fig. 8. 



3. The ordinary marrow cell is a large, colorless cell, with a 

 characteristic nucleus and a faintly granular protoplasm. The 

 nucleus is of a vesicular character, having an oval shape, a 

 doubly contoured nuclear membrane, and one or more conspic- 

 uous nucleoli. From the nucleolus a scanty reticulum stretches 

 out toward the peripheral membrane (see Fig 12, a and b). 



4. Wandering cells. These are like 3 in structure, except 

 that the nucleus, instead of being oval, is pulled out to an 



