296 DR A. J. WHITING ON THE 



the cell resembles the special uninucleated vacuolated cells. Thus the multinucleated 

 vacuolated cell seems to afford a connecting: link between the uninucleated vacuolated 

 cell and the giant cell. 



(30) The special uninucleated vacuolated cells were found in the spleens of the 

 rabbit, rat, guinea-pig, human foetus (at the seventh and at the eighth month), and 

 child. 



(31) They appear to be produced from larger or smaller giant cells, by the extrusion 

 of nuclear buds, the number of vacuoles increasing until there is little of the original 

 protoplasm left, and the amount of nuclear substance gradually diminishing. 



(32) It is doubtful whether these cells ever contain non-nucleated red blood 

 corpuscles ; but erythroblasts are occasionally seen within their vacuoles. 



PART II. 

 On the Physiology of the Spleen and Blood Formation. 



Chapter V. 



Foa and Salvioli # have shown that the nucleated red cells in the embryonic 

 liver bear a direct numerical relation with the erythroblasts and with the giant cells 

 in that blood-forming organ ; they have given reasons for believing that the erythro- 

 blasts are developed from the giant cells, or, as they term them, hsematoblasts ; and 

 they have observed similar cells, affording evidence of a similar process, in the fcetal 

 spleen and lymphatic glands. 



As regards the spleen, we have, we think, already produced confirmation of the 

 probability of the truth of the theory that its giant cells produce erythroblasts. 



If the endogenous development of erythroblasts within giant cells is an important 

 mode of blood production, one would not unreasonably expect to find the mother 

 cells in those positions where blood formation is known to be actively progressing. 



The positions in which mammalian blood formation is known to occur may be 

 summarised as follows : — 



(a) In the vascular area of the fcetal membranes. 

 (/>) Within the foetus during early intra-uterine life. 



(1) In the liver. 



(2) In the subcutaneous connective tissue. 

 (c) During late intra-uterine life. 



(1) In the spleen. 



(2) In the bone marrow. 



(3) In the lymphatic glands. 



* Foa and Salvioli (38), p. 125. 



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