THE CORPUS LUTEUM OF PREGNANCY IN SWINE. 81 



In 1910 Delestre published, from the Clinique Baudeloquo, the results of his studies 

 in this direction, using the cow as the subject of his work, on account of the fact that the 

 term of pregnancy is very nearly that of the human, being 284 to 285 days. Unfortunately 

 his youngest corpus luteum of pregnancy dated from about 2\ months, the snout-rump 

 length of the calf being 12 cm., so that he missed the very stage at which the exoplasmic 

 apparatus is at its height, if the sow's corpora lutea are like the cow's. At this stage he 

 describes four cellular elements of the corpus luteum: (1) The lutein cells, presenting no 

 particular feature. (2) Cells somewhat larger than the lutein cells, having lightly staining 

 protoplasm. I do not know what these may be, as I have not seen them in the sow. 

 (3) Plasmodial masses with 5 or 6 nuclei, destined to form young lutein cells. I have not 

 seen these in the sow. (4) Cells which, if I interpret the description rightly, are like those 

 mentioned above as additional cells of the corpus luteum, type 2. Delestre states that at 

 4 months the plasmodial masses have disappeared, giving rise to young lutein cells, which 

 are smaller than adult lutein cells, and are grouped, several together, in one mesh of the 

 connective tissue. There are now two sorts of lutein cells, one containing fat, the other 

 free of fat. At 4^ months the number of cells containing fat is augmented and the young 

 cells are rare. At 5 months all the young cells have disappeared and the adult features 

 predominate, most of the cells containing fat. At this time signs of degeneration appear, 

 in the form of vagueness of outline of some of the cells, poor staining reaction, and dried-up 

 skeleton-like nucleus. 



Delestre gives a comparative table of the characteristics of the corpus luteum at the 

 beginning and end of pregnancy, which in most particulars applies equally well to the sow, 

 although I can not confirm his account of the formation of young lutein cells from plasmodial 

 masses, nor the description of degenerating cells at such an early time. With these simple 

 outlines of the life-history of the corpus luteum as described by previous investigators, and 

 with the extensive cytological data now at hand, we have the tools for the main part of our 

 task, which is to relate the changing anatomy of the corpus luteum to the stages of advancing 

 pregnancy. 



CHARACTERISTICS OF THE CORPUS LUTEUM AT THE VARIOUS STAGES OF PREGNANCY. 



I had hoped that the gross characteristics of the corpus luteum would be of help in 

 the problem at hand, but I have been forced to the conclusion that the differentiation of 

 corpora lutea of varying ages is only to be made with the oil-immersion lens. The corpus 

 luteum of the youngest pregnancy in my series is already solid, so we gain nothing from the 

 size of the central cavity, as we might in other species, such as the human, in which the 

 cavity lingers longer. The blood-vascular system changes little during pregnancy, since 

 there is the same amount of tissue to be supplied. The color is variable and gives no dis- 

 tinction of age. Sometimes in early corpora lutea the rapid increase in volume of lutein 

 tissue causes a bulging of the inner substance of the corpus luteum through the point 

 of rupture, the so-called "Propf" of the German writers. If we find an ovary in which 

 the corpora lutea possess "Propfen," or several of the corpora contain slight remains of the 

 former central cavity in the form of small spaces containing old blood, then probably the 

 ovulation was fairly recent; but, on the other hand, in pregnancies of the first month the 

 corpora lutea are often solid and homogeneous. 



We must resort, then, to the immersion lens and a study of finer histological details. 

 Because it will make the results more convincing, I shall mention briefly the method by 



