THE CORPUS LUTEUM OF PREGNANCY, AS IT IS IN SWINE. 



INTRODUCTION. 



At the instance of Professor Mall, I have undertaken the studies to he presented in 

 this paper, in the hope of gaining such knowledge as would enable us to draw up a standard 

 description of the corpus luteum throughout its history. If we knew the exact appearance 

 of the human corpus luteum at all its stages, especially during pregnancy, we should have 

 an instrument of the greatest value in the solution of many complicated problems of 

 embryology and physiology, and even of clinical gynecology and organotherapy. Since 

 the path of such a research as I have here begun is as yet unblazed, and because studies of 

 the human tissues are so hampered by pathological changes, faulty histories, and difficulties 

 of collection and preservation, for the beginning we have limited ourselves to the ovary of 

 the domestic sow, and have started out with the simple hope of obtaining an answer to one 

 question: What is the appearance of the corpus luteum at each and every stage of preg- 

 nancy? To this query as simple an answer has been found, but the work has led in such 

 unexpected directions and into such interesting by-ways that the reader will no doubt feel 

 as much disappointment in reading as the author has in writing a paper which answers one 

 question, only to raise a score as yet unsolved. 



During the months of October 1913 to May 1914 I have collected from the hundreds 

 of sows' uteri and adnexa obtained at the slaughter-house adjacent to this laboratory, 128 

 pairs of ovaries from pregnant animals, the embryos being in each case examined and 

 measured. The youngest embryo studied had 5 somites, and its age was estimated at about 

 15 days. The specimen is preserved as pig embryo No. 10 in the embryological collection 

 in this laboratory. The oldest fetus in my series was 290 mm. long, or just about at term. 

 In this paper, where lengths are given, they represent careful crown-rump measurements. 

 Since the age-length ratio of embryos of the pig has never been fully worked out, the ages 

 given are only approximate, and were obtained, for the younger stages, by comparison with 

 Kernel's lists and figures (1897), and for the older stages from a table found in Strange- 

 ways' "Veterinary Anatomy," and said to have been compiled from the works of Gurlt, 

 Leyhs, Franck, and others. The entire uteri and adnexa were received at the laboratory 

 within an hour after killing, generally within a few minutes, and while yet warm. The 

 fixing agent used was 10 per cent aqueous solution of formalin (40 per cent formaldehyde). 

 The preparations were made by cannulating the ovarian artery, or the uterine, in which 

 latter case it was advisable to tie off a few branches. The blood-vessels of the ovary were 

 then injected with the formalin solution heated to 40° to 50° centigrade, and were placed in 

 the same fluid. In a few cases where injection was not possible or not successful, the cor- 

 pora were sliced with a razor-blade and the ovaries immersed in the warm formalin. For 

 the study of the fat-content of the tissue, slices were cut from certain of the fresh corpora 

 lutea and fixed in 2 per cent osmic acid for 24 hours. In all cases the ovaries were numbered 

 consecutively, the right and left ovaries being indicated, the embryo pigs were measured, 

 and the number of them in each horn of the uterus recorded. 



The specimens were left in the formalin 24 to 48 hours, the solution having been allowed 

 to cool an hour or two after immersing the specimens. After fixing they were washed in 

 running water 24 hours, then dehydrated by passing through graded alcohols for 24 hours 

 each (30, 40, 50, 60, 65, 70, 75, 80 per cent). The whole ovaries were then placed in 



