130 CYCLIC CHANGES IN THE OVARIES AND UTERUS OF THE SOW, ETC. 



present the remainder of the ovarian substance is dwarfed in comparison. At this 

 stage the corpora are nearly always solid, though at times one or two in an ovary 

 may remain slightly cystic. The cut surface bulges from the capsule and presents 

 a somewhat velvety texture of pink color without trace of the yellow and orange 

 pigments which are so characteristic of the corpus luteum in the bovine and human 

 ovaries. The consistence of the corpus luteum at this time is not unlike that of the 

 pig's liver. 



In microscopic sections (fig. 3, pi. 1; fig. 12, pi. 2) the granulosa lutein cells 

 form the most conspicuous element of the tissue, since they are distinguished both 

 by their large size (reaching the diameter of 30 to 40 micra) and by the elaborate 

 cytoplasmic patterns which they contain after fixation in slow aqueous fixatives 

 like formol, Bouin's picro-formol-acetic fluid, etc. As previously described (1919), 

 the granulosa lutein cells of certain species contain a large amount of a lipoid or 

 mixture of lipoids, probably associated with proteins, which is sufficiently oily to 

 round up into droplets when the tissue is submitted to the action of water. The 

 droplets thus produced usually surround the pre-existing globules of neutral fat, 

 which are also present in considerable numbers in the granulosa lutein cells of swine, 

 but these latter are readily removed by the alcohol, ether, and xylol of the usual 

 histological procedures, and hence the final appearance is usually such as shown in 

 figure 12 (gr. I. c.), in which the lipoid droplets are seen as hollow spheres (ap- 

 pearing as rings in thin sections) more or less retracted from the surrounding cyto- 

 plasm. The bodies in question are not seen in fresh tissues, nor in cells fixed very 

 promptly in rapid coagulants like osmium tetroxide, which presumably precipitate 

 the proteids before the oil droplets round up. The appearances described, there- 

 fore, are simply the result of methods of fixation which do not preserve certain 

 obscure lipoids in their natural diffused state ; but the artifact has proved useful in 

 several ways, notably in tracing the history of the granulosa derivatives. 



Besides the granulosa lutein cells and the blood-vessels, the corpus luteum 

 contains cells of another type, whose origin has been traced by the author to the 

 theca interna of the Graafian follicle. Corpora of the eighth to the tenth day 

 always contain a few distinct clumps of theca interna cells in their original position 

 about the periphery of the corpus luteum and along the vessel-bearing septa which 

 pass radially inward where the follicle- wall was infolded by collapse at ovulation. 

 Many others of the theca cells, however, have wandered among the granulosa 

 lutein cells, from which they can usually be distinguished by smaller size (diameters 

 of 10 to 25 micra), by a more deeply staining cytoplasm, which is often densely 

 packed with minute regular vacuoles, giving a characteristic foamy appearance, 

 and (in osmium preparations) by the presence of plentiful fat globules which vary 

 greatly in number and size (fig. 13, pi. 2, th. I. c.). The theca lutein cells often 

 have squared or irregular outlines, fitting into the interstices between the swollen 

 rounded surfaces of the larger granulosa lutein cells (fig. 12, pi. 2, th. I. c.). 



The tissue is held together by a framework of reticular connective fibrils 

 which, as illustrated in figure 4, plate 1, from a preparation by Bielschowsky's 

 method, form a dense network about all the lutein cells. In view of the apparent 



