234 TRANSACTIONS OF THE CANADIAN INSTITUTE. [VoL. II. 



shown with the chromatin loops alone colored grass-green while the 

 cytoplasma and, if present, the caryoplasma are colored, in contrast, light 

 red. There is evidently no derived or modified chromatin here and the 

 only substance related to it must be situated in the chromatin loops. I 

 saw, indeed, in a number of other examples of dividing haematoblasts 

 that there was a grass-green substance between the usual chromatin 

 loops and this substance which was, evidently, modified chromatin, 

 varied in quantity from that condition where it was scarcely detectable to 

 that where it was so abundant as to obscure the outlines of the similarly- 

 stained chromatin loops. The latter condition is, certainly, a later stage 

 than that shown in Fig. 8 and the nucleus of the fully formed red cell, in 

 all probability, represents the culmination phase of the conversion of 

 chromatin into hjematogen. 



The chromatin of haematoblasts can be shown to be different in 

 composition from that of an ordinary cell. In order to demonstrate this 

 one must resort for material to those Amblystoma larvse in which the 

 majority of the blood corpuscles are more or less pigmented. The 

 latter condition can be readily determined by putting the larva in water 

 on a glass slide and examining its gills through the low power of the 

 microscope. Indeed almost any larva, not very long after its escape from 

 the envelope, will answer the purpose. It is fixed in Flemming's Fluid for 

 half an hour, then put in 5o7o alcohol for fifteen minutes, afterwards in 

 70% fi^r twenty-four hours and finally in 95% for four or five hours. If 

 it is stained in toto with alum-haematoxylin, imbedded in paraffin, 

 sectioned, and the sections mounted in series on the slide in benzol 

 balsam, one can in the concave sides of the aortic arches and in the 

 developing spleen find a large number of dividing hci^matoblasts which 

 at once betray their presence by the dull slate, or slate-brown color 

 which their chromatin possesses, while the chromatin of ordinary cells is 

 stained a tint between purple and navy-blue. Figs. 9 a and b are 

 contrast drawings made from specimens in the concave side of the same 

 aortic arch and in the same section, the one representing an endothelial 

 cell, the other a haematoblast. In the latter the slate-brown color of 

 the cytoplasma was not very marked and this may frequently be 

 found free from any color whatever. No more decisive proof could be 

 given that the chromatin of haimatoblasts differs chemically from that 

 of ordinary cells. That which gives with the haemato.xylin a slate-brown 

 color is probably a haematogen or haematogenous chromatin. 



Flemming* has noticed this reaction of the chromatin of the haemato- 

 blasts on the haematoxylin, and he states that dividing haematoblasts 



* Arch, fur Mikr. Anat. Bd. XVI., p. 396 and Taf. XVII., Figs. 19 and 20. 



