144 VICTOR E. EMMEL 



blasts are found in which there has occurred a division of the nu- 

 cleus into two parts, or a fragmentation into even a larger number 

 of subdivisions. It has been assumed that a subsequent expulsion 

 of only a part of the nucleus at a given time might thus result in 

 a partial discing or cupping of the erythroblast, though the cell 

 may still retain a nuclear remainder. Such an explanation, at 

 least for the pig embryo, does not appear tenable for the following 

 reasons. First, no evidence was noted indicating that the nuclei 

 in the typical disc or cup-shaped cells were only remnants of pre- 

 viously divided and partially extruded nuclei, and second, it has 

 been possible in the pig embryo to find occasionally such double 

 nucleated erythroblasts, and they too, it is to be emphasized, 

 had already assumed disc or cup forms as is illustrated in figures 

 12 a, 23 and 24. It seems clearly evident, then, that the as- 

 sumption of the cell shape under consideration is by no means 

 necessarily correlated with an extrusion of the nucleus. Wei- 

 denreich.('03 a), in a discussion of Dekhuyzen's observation of 

 bell-shaped corpuscles in Petromyzon fiuviatilis indicates an appre- 

 ciation of this possibility in the remark ''interessant ware dabei 

 jedenfalls, dass auch kernhaltige rote Blutkorperchen gabe, die 

 die Glockenform aufweiasen, moglicherweise sie also keine Folge 

 des kernverlustes zu, sein braucht; selbstverstandlich bedarf dies 

 aber noch besonderer Untersuchung" (p. 475). " 



While the present facts, therefore, indicate that the assump- 

 tion of a disc or cup form by the mammalian red blood corpuscle 

 is not necessarily initiated by nor dependent upon the extrusion of 

 the nucleus, the question may be considered whether there are 

 any other factors which may account for the phenomenon. There 

 is a substantial and growing body of facts not only for the conclu- 

 sion that the mature erythrocyte is surrounded by a membrane 

 (Weidenreich '05, p. 444, 445 and '11, p. 27) but also that this 

 membrane is composed in part at least of lipoid substances such 

 as lecithin and cholesterin. For example, Peskind ('03), after a 

 study of the action of acids and acid salts on blood corpuscles, 

 concludes that ''theoretical considerations, as well as chemical 

 and histological facts brought out in this paper, render the exist- 

 tence of an envelope in the mammalian corpuscle highly prob- 



