142 VICTOR E. EMMEL 



cytoplasmic pole in contrast to the region containing the nucleus 

 or nuclear pole. In other words, in this reaction while the cyto- 

 plasmic pole of the disc has become smaller and rounded out, 

 the nuclear pole has undergone but little modification. In some 

 cases the contrast between these two poles is even further marked 

 by a paler appearance in the fresh unfixed preparations, of the 

 nuclear pole as compared with the opposite yellower hemoglobin 

 containing cytoplasmic pole. Incidentally, it is a matter of fur- 

 ther interest to note that the profile views of such cells may present 

 appearances deceptively approximating one of nuclear extrusion 

 which, as a precaution, should possibly be taken into account in 

 evidence advanced for denucleation by a process of extrusion. 



This striking difference in the behavior of the two poles of the 

 erythroblast appears indicative of corresponding differences in 

 morphological structure. It is generally recognized that the red 

 blood corpuscle is composed of two parts, the one, consisting 

 chiefl}^ of a solution of hemoglobin and the other, the so-called 

 stroma or colorless part. There has been considerable discussion 

 as to whether, in the case of the non-nucleated erythrocyte, this 

 stroma does or does not permeate the whole corpuscle as a 

 cytoplasmic framework. One of the characteristic arguments ad- 

 vanced against the former of the two possibilities is based upon the 

 changes in form which the biconcave disced corpuscles undergo 

 when brought into contact with water, that is, into a hypertonic 

 solution. Upon the absorption of water under such circumstances, 

 the concave sides of the disc swell out and the corpuscles assume a 

 spherical form. It is stated that, 



This simple experiment conclusively shows that the corpuscle is com- 

 posed of a membrane or external envelope with colored fluid contents. 

 . . . . On the other hand it is inexplicable on the supposition 

 that the corpuscle is composed of a uniform disc-shape stroma permeated 

 with colored substance, .... for if this were the case, water 

 should swell it out uniformly, as happens if a disc of gelatine is placed in 

 water — the whole disc imbibing the water, and becoming increased in 

 size while retaining its original shape (Schafer '12, p. 369). 



The extension of a similar argument to the reactions under con- 

 sideration in the erythroblasts leads to the conclusion that there 

 are important structural differences between the two poles of the 



