No. I.] BLOOD CORPUSCLES. eg 



described by Kolliker and by Neumann as the first stage in 

 the disappearance of the nucleus. In foetal cats I have found 

 nucleated red corpuscles in the blood even at birth, though they 

 were few in number. In cat foetuses of an earlier age they 

 are proportionally more numerous. The youngest cat embryo 

 which I examined was one measuring 2.5 cms. from the crown 

 of the head to the root of the tail. A drop of its blood taken 

 from the heart and stained in methyl green (a i per cent solu- 

 tion in 0.6 per cent NaCl) showed a number of interesting 

 things which, so far as I know, have not been noticed, or at 

 least not dwelt upon before. In the first place, there were two 

 distinct forms of red corpuscles present in the blood : one, 

 large, oval, and nucleated, resembling somewhat the corpuscles 

 of the reptiles or amphibia. In shape, they were biconcave, 

 irregular, or apparently, in some cases, biconvex, and were so 

 extremely plastic as to appear semi-liquid. When treated with 

 staining reagents, they took on an oval biconvex form. These 

 corpuscles were distinguished, moreover, by the deeper tint 

 of the haemoglobin which they contained. Their nuclei were 

 variable in size, were usually placed eccentrically, and were 

 characterized by the fact that without exception in the em- 

 bryo of this age they stained a homogeneous bluish color 

 with the methyl green, showing no trace of nucleoli or intra- 

 nuclear network. The size of these corpuscles in their long 

 diameter varied from about two to four times the diameter 

 of the red corpuscle of the adult mammal. The second form 

 was circular in outline and of the usual size of the cat corpus- 

 cles — some of them were nucleated, and some had lost their 

 nuclei (see Fig. i). The nuclei of the nucleated forms were 

 in some cases stained a uniform green blue color from the 

 methyl green, like the oval corpuscles just described; but in 

 other cases the nuclei showed an intra-nuclear network or 

 granulation. It is worthy of special emphasis that all the red 

 corpuscles which were non-nucleated belonged to this class. 

 Diligent search through a number of preparations failed to 

 reveal a single large oval red corpuscle which did not have a 

 nucleus.^ 



1 After this article was in the hands of the printer, Hayem's extensive work on 

 the blood, " Du Sang et de ses Alterations Anatomiques, 1SS9," came into the 

 author's possession. In it is found a reference to these large corpuscles. He 

 speaks of them as giant nucleated corpuscles, discoid and concave in shape, though 

 occasionally irregular and flat or subglobular. 



