No. I.] BLOOD CORPUSCLES. n^ 



The number, of course, may not be constant, at least not for 

 different conditions of life. All that one can actually observe, 

 and this point I wish to emphasize, is that the cells which 

 I have described as the mature and immature forms of the 

 nucleated red corpuscle really exist in the marrow at all times, 

 that the latter undoubtedly multiply by karyokinesis, and that 

 the former bear every indication of being nearer the condition 

 of the non-nucleated red corpuscle, both in size and depth of 

 color, and in the fact that they are no longer capable of repro- 

 duction. The theory which I have suggested offers a simple 

 explanation of these phenomena. One other hypothesis which 

 might be suggested, and which has in fact been proposed, is 

 that the nucleated red corpuscle, after it has been formed from 

 the erythroblast by the development of haemoglobin, begins to 

 undergo a process of condensation which results in making 

 both the cell and the nucleus smaller. But this theory does 

 not take into consideration the fact that what I have called 

 the younger forms of the nucleated red corpuscle are without 

 doubt capable of active multiplication, and that the offspring 

 seem to show in general a diminution in size and a definite 

 change in the character of the nucleus. 



The Tratisformation of the Nucleated Red Corpuscle to the Red 



Corpuscle of the Blood. 



The essential factor in the transformation is the loss of the 

 nucleus. After it was known that in the foetus the nucleated 

 red corpuscle loses its nucleus and changes to the non-nucleated 

 form, Kolliker (3) proposed the theory that the nucleus is de- 

 stroyed by absorption within the cell. The absorption may be 

 preceded by a fragmentation of the nucleus more or less com- 

 plete, such as one often sees in examining the blood of a young 

 embryo. Kolliker does not seem to have given any microscopic 

 proof for his view other than the partial disintegration of the 

 nucleus. Neumann {'^b), after he had clearly shown that the 

 nucleated red corpuscle exists also in post-natal life as the pre- 

 cursor of the non-nucleated form, adopted the theory of Kolliker 

 to explain the disappearance of the nucleus. He was able to 

 follow the process best in the human foetus (five months), and 

 describes the nucleus as becoming smaller, more homogeneous, 

 and finally notched or indented. In addition, he describes red 



