564 SWALE VINCENT 



and Surface,' who injected corpus luteum extract into fowl and pre- 

 vented ovulation (vide supra). 



As pointed out by Loeb, the acceleration of ovulation produced through 

 extirpation of the corpora lutea is limited. The next ovulation has to 

 await the maturation of follicles. Without the presence of mature fol- 

 licles, a new ovulation cannot take place, even in the absence of corpora 

 lutea. 



Another discovery has been made as a result of experiments involving 

 extirpation of the corpora lutea. The idea that the corpus luteum might 

 provide an internal secretion subserving the fixation of the ovum in the 

 uterus was first conceived by Gustav Born, and bequeathed to Frankel 

 to work out. This author (1901-03) came to the conclusion that the 

 corpus luteum ministers in some way to the needs of the gravid uterus. 

 A series of experiments upon rabbits was carried out, the ovaries being 

 removed at intervals varying from one to six days after the occurrence 

 of coition. The rabbits were killed and it was found that the extirpation 

 of the ovaries had prevented the fixation of the embryos or had caused 

 abortion. In other cases the yellow bodies were cauterized out, and 

 similar results were obtained. 



Marshall and Jolly extirpated the ovaries from pregnant dogs and 

 rats. In the dogs ovariotomy was performed at intervals of from three 

 days to four weeks after impregnation. The pregnancy was discon- 

 tinued in every case except one, in which a portion of the right ovary, 

 which contained the degenerate remains of two undoubted corpora lutea, 

 was found post mortem, three days after parturition, when the dog was 

 killed. In this experiment ovariotomy was performed three days after 

 copulation, and parturition occurred fifty days subsequently. Only a 

 single pup was produced, and birth was premature. The pup died after 

 being suckled normally for three days. In rats pregnancy was not con- 

 tinued in any case in which ovariotomy was preformed during the first 

 six days of pregnancy. In other cases, in which the ovaries were removed 

 at periods from the sixth day until near the end of pregnancy, the young 

 were produced normally at full term. Control experiments were also 

 carried out, in which the abdominal cavity was opened up during an 

 early stage of pregnancy and the ovaries cauterized, or in which one 

 ovary was removed and not the other, and in these experiments the course 

 of pregnancy was not interfered with. Marshall and Jolly did not 

 attempt to remove only corpora lutea, while leaving the rest of the ovary. 

 Their experiments 'fully confirm those of Frankel. 



Marshall points out that there is no evidence that the corpus luteum 

 governs the fixation of the embryo otherwise than by stimulating the 

 uterine mucous membrane to hypertrophy. The general conclusions of 

 Frankel (&) and of Marshall and Jolly have since been confirmed by sev- 

 eral authors. 



