CYCLIC CHANGES IN UTERUS AND OVARIES. 29 



might arise. It is probable that in those cases secondary changes, 

 due to embedding of an ovum which was not followed by normal 

 embryonic development, had taken place in the mucosa. Only 

 in one case there might be some doubt as to whether the typical 

 cyclic changes had not taken place in the uterus notwithstanding 

 the presence of pregnancy. 



As to the way in which pregnancy influences the uterine mu- 

 cosa, it is probable that the activity of the living decidual cells 

 prevents the proliferation of the uterine mucosa. It cannot be a 

 mechanical effect of pull on the uterine wall thourgh the ovisac 

 because the uterus of a nonpregnant horn behaves in a similar 

 manner as the pregnant horn. If ovulation takes place after 

 an experimentally produced placentoma has become necrotic 

 the typical cyclic changes of the uterus follow ovulation, as in 

 the following experiments: 



No. 1 152. Six days, twenty and one half hours after copulation, 

 cuts were made into the uterine wall ; examination nineteen days 

 later (twenty-five days, twenty and a half hours after copulation). 

 In the ovaries we found just ruptured follicles. There were 

 present corpora lutea which were beginning to become vacuolar 

 and to shrink (the corpora lutea of the former generation). 

 Small good follicles as w^ell as follicles with granulosa degeneration 

 into which connective tissue began to grow were seen. These 

 conditions indicated that ovulation had taken place withjn the 

 previous twenty-four hours. The left uterus above the nectoric 

 placentoma showed high cylindrical epithelium with a hyaline 

 basal area. At some places the epithelium is lower as a result of 

 pressure. The glands have high or medium cylindrical epithe- 

 lium. There are some dilated gland ducts filled with poly- 

 nuclear leucocytes. No mitoses are present in the surface 

 epithelium and only a few in the gland ducts. At some places 

 polynuclear leucocytes migrate into the surface epithelium and 

 disintegrate into small chromatin particles. The structure of the 

 uterus corresponds therefore to the condition found approximately 

 within the first thirty-six hours after ovulation. The condition 

 of the ovaries and of the uterus correspond to each other. 



Also in another guinea-pig (No. 1140) the presence of necrotic 

 placentomata in both horns of the uterus did not prevent the 



