No. I.] BLOOD CORPUSCLES. 87 



Origin of the Nucleated Red Corpuscle. 



Most authors agree that the nucleated red corpuscle is de- 

 rived from a colorless cell existing in the marrow, but there is 

 considerable difference of opinion as to the characteristics and 

 origin of this cell. Lowit (29), it will be remembered, gives 

 to it the name of erythroblast, and describes certain histologi- 

 cal characteristics which enable him to recognize the cell 

 wherever seen. Others derive the nucleated red corpuscles 

 from what are known as the ordinary marrow cells, and others 

 still, as Osier (28), describe a peculiar kind of cell in the mar- 

 row from which the nucleated red corpuscles are derived, and 

 which correspond more or less closely to the erythroblasts of 

 Lowit. Before speaking of my own view, it will be necessary 

 to describe briefly the different sorts of cells found in the red 

 marrow of the cat. In teased specimens of the marrow we 

 meet, in the first place, with the morphological elements of the 

 blood, the red corpuscles, white corpuscles, both uninucleated 

 and multinucleated, and the blood plates. Of the marrow ele- 

 ments proper, we have, first, the nucleated red corpuscle. By 

 this term is meant a nucleated cell colored with haemoglobin. 

 The size of these cells is quite variable, and they are fre- 

 quently found in different stages of cell division, as described 

 by Bizzozero (igd), the most common figure being the diaster. 

 But the most marked peculiarity in the structure of the nucle- 

 ated red corpuscles is found in the nucleus. In some of these 

 cells, which for the sake of clearness I will speak of as the 

 immature nucleated red corpuscles, the nucleus is characterized 

 by an intra-nuclear network of chromatin, at the nodal points 

 of which are found conspicuous granules of a similar material, 

 which stain, however, more deeply than the reticulum. In 

 badly preserved specimens, therefore, the nucleus seems to be 

 composed of a number of fine or coarse granules imbedded in 

 a clear or slightly colored matrix. The cell protoplasm of 

 these immature forms is, as a rule, only slightly tinged with 

 haemoglobin, and makes a relatively thin envelope round the 

 nucleus (see Fig. 8). Others of the nucleated red corpuscles, 

 which may be distinguished as the mature forms, have a nucleus 

 which shows no sign of a reticulum when stained with methyl 

 green, haematoxylin, saffranin, etc. The nucleus, when stained, 



