ERYTHROBLASTS IN THE PIG EMBRYO 1(55 



of the pig embryo blood, it may be stated that while some hemoly- 

 sis may be taking place at all stages of the experiments, in the 

 more successful cultures there is little evidence of it until at 

 least after the second day or later, as indicated by the presence 

 of the so-called 'shadow' as well as by the color of the plasma in 

 both fresh and fixed, stained preparations. If proper care be 

 taken cultures can be made containing only a few, if any, crenated 

 cells. Occasionally broken or bursted hemolyzed corpuscles may 

 be found in the older cultures. Concerning fragmentation, those 

 instances in which the corpuscles, whether nucleated or non-nucle- 

 ated, were observed to become subdivided into a number of smaller 

 pieces approximating the size of blood platelets may possibly come 

 under this classification. Such a fragmentation may also occur 

 in the cytoplasm of the nucleated portion remaining after the 

 separation of the original erythroblasts into two parts, A third de- 

 generative change consisted in the appearance of what were appar- 

 ently vacuoles in the cytoplasm. In a number of instances this 

 was seen to occur while the given corpuscle was under observation. 

 The movement of one such vacuole has already been described (p, 

 147). Figure 34 illustrates how such a vacuole may become 

 divided into two parts. In this case it will also be observed that 

 the larger of the two subdivisions apparently broke through the 

 surface of the cytoplasm, although it is possible there still re- 

 mained between the vacuole and the exterior of the cell a mem- 

 brane invisible in the unstained corpuscle. It is of interest to 

 note that this behavior of the vacuoles is suggestive of the vacuoli- 

 zation of erythrocytes in the mesenchyme of the human embryo 

 as described by Minot ('12 p. 512, and corpuscle h, in fig. 361), 

 All of these degenerative changes are most marked in the older 

 cultures, in homoplastic cultures, and in those experiments in 

 which the plasma had been modified by the addition of Ringer's 

 solution or water. 



In resume it may be said that the behavior and cytological 

 characteristics of the erythrocytes seem to indicate that the cul- 

 ture conditions approximate normal conditions sufficiently to 

 justify the expectation that in such cultures it should be possible 

 to obtain some manifestation of the normal transitional stages in 



