30 LEO LOEB. 



development of the typical cyclic changes in the uterus. In 

 this case cuts had been made into both horns of the uterus six 

 days, six and a half hours after copulation. Nineteen days later, 

 twenty-five days, eight and a half hours after copulation, we find 

 on examination the presence of necrotic placentomata. Some 

 small areas of the placentoma were still alive. Condition of the 

 ovaries showed that ovulation had taken place about five days 

 previously. Correspondingly we find in the uterine mucosa a 

 cell layer with mitoses in connective tissue cells and some mitoses 

 in gland fundi. The surface epithelium is cuboidal to cylindrical 

 and contains some mitoses, perhaps as a result of the regenerative 

 changes which are taking place at that time. 



Pregnancy seems also to prevent the changes in the uterus 

 which accompany the period of heat. This we found in guinea- 

 pig No. 1300 in which three days, eighteen hours after copulation 

 the thyroids had been extirpated. Examination seventeen 

 clays, nineteen and a half hours after copulation showed that this 

 did not interfere with the development of the typical cyclic 

 changes in the ovaries. They present the picture characteristic 

 of this period. There are present several fully matured follicles 

 ready to rupture, but the corpora lutea of pregnancy which do 

 not show any sign of vacuolization and have vessels with well 

 developed walls, prevent this rupture. We should expect under 

 those conditions (period of time, presence of mature follicles) in 

 a non-pregnant uterus high cylindrical epithelium of the surface 

 and of the gland ducts, lower gland fundi, the nuclei of the con- 

 nective tissue somewhat large and vesicular. Instead, we find 

 the typical picture of the uterus during pregnancy; low cuboidal 

 epithelium of the surface with a few isolated mitoses, low glands 

 without mitoses, fibrillar connective tissue with small nuclei. 

 At some places transudate raises the surface epithelium from the 

 underlying connective tissue. Is it not probable that extirpation 

 of the thyroids prevents the uterine changes accompanying heat 

 because we observed the occurrence of these changes in another 

 guinea-pig in which the thyroid had been removed previously. 

 We may, therefore, conclude that the presence of pregnancy 

 prevents those changes in the uterus which accompany the 

 period of heat. And it appears probable that pregnancy prevents 

 also the psychical changes characteristic of the state of heat. 



