CYCLIC CHANGES IN UTERUS AND OVARIES. 37 



necrosis was found in the placentoma; no mitoses, or only 

 exceptional mitoses were found. Under certain conditions we 

 observed however in the placentoma an amitotic proliferation of 

 nuclei which may lead to the formation of giant cells. The living 

 parts of the placentomata were hyaline and partly vacuolar. 



Extirpation of the ovaries six to eight clays after copulation 

 does not prevent, therefore, entirely the production of placen- 

 tomata through incisions made into the uterus simultaneously 

 with the castration, but it reduces very much the cell proliferation 

 and may cause a partial early necrosis. 



We found also that extirpation of the corpora lutea six to eight 

 days after copulation led to the production of placentomata 

 which were smaller than usual. It. is however possible that 

 extirpation of the ovaries has a still more strongly inhibiting 

 action on the growth of the placentomata than removal of the 

 corpora lutea. 



In several other series of experiments the ovaries were extir- 

 pated at periods following the incisions into the uterus. If the 

 incisions into the uterus were made about six days after copu- 

 lation, the ovaries extirpated two days later and the examination 

 made eight or ten days after the last operation, placentomata 

 developed in all cases, but their size varied. In one case they 

 were of medium size, but usually they were smaller than normal. 

 The amount of necrosis and hemorrhage also varied; these 

 changes could be very insignificant or they could be very con- 

 siderable. 



In another series incisions were made into the uterus about six 

 days after copulation; seven days later the ovaries were extir- 

 pated and seven days after castration the examination was 

 made. In these experiments the placentomata were therefore 

 fourteen days old at the time of examination, and the ovaries 

 were extirpated at a time when the placentomata had already 

 formed. The placentomata were found almost entirely necrotic; 

 some small living areas were present usually directly under the 

 outer surface of the placentoma or near the mucosa, both 

 places where the nourishment was still better. No mitoses 

 were seen in the living part of the placentoma. 



In the surface epithelium of the mucosa and in the glands of the 



