PATHOLOGIC OVA, ALBINO RAT 123 



lobules of the same nucleus. In A of this figure there is shown 

 to the lower left of the large cell another relatively large cell, 

 enclosing a globular inclusion, which stained faintly, and the 

 nature of which was not fully determined. In the upper part of 

 each of the two figures are seen cells which show cytolysis and 

 loss of nuclei; regarded as degenerating cells. When compared 

 with the normal blastodermic vesicles obtained from the same 

 uterus, the ovum here described presents a unique appearance, 

 and was readily recognized as showing development and structure 

 which deviated from the normal. At this stage of development, 

 the blastodermic vesicles of the albino rat are still found lying 

 free in the lumen of the uterus, showing no structural relation to 

 the uterine mucosa. This vesicle has been interpreted as show- 

 ing irregular or retarded segmentation. It is conjectured that 

 one of the cells, perhaps of the 8-cell stage, did not undergo 

 further cleavage. The large cell presents an appearance evidenc- 

 ing beginning stages of degeneration, and in further development, 

 would probably have undergone dissolution. The majority of 

 the smaller cells of the roof appear as if normal, as do also the 

 cells of the floor, certain of the smaller cells of the floor presenting 

 mitoses as evidence of further proliferation. 



In figure 4, A, B, and C, there are presented typical sections 

 of three ova of the albino rat showing what has been regarded as 

 irregular segmentation. A of this figure represents an ovum 

 taken from rat No. 64, 4 days, 14 hours, after insemination, in 

 the uterus of which there were found five normal ova showing 

 early stages of blastodermic vesicle formation, four of which are 

 cut longitudinally, one in a series of cross-sections. In each of the 

 four longitudinally cut series the floor of the respective vesicles 

 is markedly folded, owing to fixation contractions; therefore, 

 none were sketched as normal stages. In appearance, they re- 

 semble closely the vesicles sketched under C, D, and E of figure 

 20, Part I. In the pathologic ovum, shown in A of figure 4, 

 there is no evidence of segmentation cavity formation. How- 

 ever, the ovum cannot be regarded as presenting a late morula 

 stage such as is figured in A of figure 20, Part I, since it shows 

 distinct departure from the normal. The marked constriction 



