4O LEO LOEB. 



It is therefore probable that they are in some way responsible 

 for the changes in the uterine mucosa accompanying heat. Even 

 if extirpation of these follicles should not prevent the occurrence 

 of heat, this would not be conclusive evidence against this 

 assumption inasmuch as the mature follicles had already had an 

 opportunity at the time of extirpation to exert their influence. 

 In a similar manner we have shown previously that extirpation 

 of the corpora lutea five to six days after ovulation does not 

 prevent the production of placentomata, while extirpation done 

 one day after ovulation has a preventive effect. There still 

 remains of course the ordinary follicles as the possible source of 

 the energy leading to these changes in the uterine mucosa; 

 inasmuch as they are present equally at other times of the sexual 

 cycle, while the mature follicles are present only at certain 

 periods and especially at the time of heat or immediately pre- 

 ceding heat, it is more probable that the mature follicles are 

 responsible for these changes. Whatever the part of the ovary 

 may be that brings about these changes, there must be added 

 to this positive factor two negative ones, namely the absence of a 

 fully functionating corpus luteum and of pregnancy, these 

 conditions being necessary for the development of the normal 

 and complete sexual cycle. 



As we saw, the ovaries have still another function, namely that 

 of maintaining the full size of the uterus. After castration various 

 constituent parts of the uterine wall diminish in size. 



VIII. SUMMARY. 



I. The cyclic changes in the epithelial as well as connective 

 tissue structures of the uterus during heat preceding copulation 

 and the changes following copulation are described ; the influence 

 of polynuclear leucocytes in these changes is shown. The latter 

 are present during the first two days following copulation. The 

 decidual cells originate from the connective tissue cells of the 

 mucosa. 



Various periods of the sexual cycle are characterized through 

 the shape and mitotic proliferation of various epithelial and of 

 the connective tissue cells. From the sixth to the twelfth clay 

 after ovulation mitoses are usually absent in the epithelial 



