ORIGIN OF THE CORPUS LUTEUM 153 



membrana propria (fig. 10). The theca externa is of course 

 drawn into the folds of the wall, and where these folds are very- 

 deep, long spindle-cells of the externa may thus penetrate almost 

 to the center of the former follicular cavity — though of course 

 they are walled out by the inner layers (fig. 9). Dividing cells 

 are found not infrequently in the theca externa, but are quite 

 rare in the inner layers. The distribution of lipoid substances, 

 as indicated by the use of osmium tetroxide and Herxheimer's 

 stain, is exactly as in the mature unruptured follicle (fig. 10, b). 

 Leucocytes are found in the walls of all developing corpora lutea. 

 The blood-vessels are exactly as in the unruptured follicle, the 

 picture presented by them being modified only by the elaborate 

 infolding of the walls (fig. 12). At the point of rupture the torn 

 vessels of the thecal plexus present to the outside, and within a 

 few days of rupture have sprouted into a little rosette of capillaries 

 about the stigma, which helps to make this spot conspicuous by 

 its redness. In the production of the curious torn spaces of the 

 theca interna, described above, vessels of the theca interna are 

 not infrequently ruptured, with resultant haemorrhage into the 

 theca. If the loss of blood is very slight, the broken-down blood 

 is taken up by the large cells of the theca interna, in which the 

 phagocyted golden-brown pigment may remain for some days at 

 least (fig. 13) . In one of my cases there was a single local haemor- 

 rhage into the theca externa, and the nearest cells of the theca 

 interna were full of blood-pigment granules. However, when the 

 thecal haemorrhages are large, the resultant haematomata may 

 burst through the granulosa into the cavity. I am inclined to 

 think that we have here the source of most of the bleeding into 

 the early corpus luteum cavity. The now almost forgotten doc- 

 trine of Henle and Paterson, that the corpus luteum is formed 

 from the blood clot of the newly ruptured follicle, naturally led 

 to investigations into the importance and constancy of the haem- 

 orrhage in various species, which have been summed up by So- 

 botta in his paper of 1896. In the pig, Zwicky ('44) held that 

 bleeding is frequent, Paladino ('80) that it occurs in two-thirds of 

 the cases, Benckiser ('84) that it is inconstant, Spiegelberg ('65) 

 that it is important, and Bonnet ('91) that it is constant and 



