INTERNAL SECRETION OF CORPUS LUTEUM i8i 



Distribution of the ccstnts-i)ihibiting Jwnnonc. According to 

 Hisaw (304), the corpus luteum is the primary source of the 

 oestrus-inhibiting hormone, but it may be detected in the blood 

 of the pregnant rabbit, guinea-pig, sow, cat, dog and mare, 

 and in the maternal and foetal sides of the rabbit placenta. 



Properties of the cestr its-inhibiting hormone. Although little 

 precise experimental work has yet been performed, it is possible 

 to deduce from the methods which give active extracts certain 

 of the fundamental properties of the oestrus-inhibiting hormone. 

 There can be little doubt that the active principle is soluble in 

 organic solvents such as alcohol, and there is good reason for 

 supposing that its thermo-stability is low. Hisaw (304) states 

 that the resistance to acid and alkali is poor, while Parkes and 

 Bellerby's original extracts seem to show that oxidization is very 

 rapid. It is fairly evident, therefore, that this oestrus-inhibiting 

 hormone is not easy to handle, and its delicate nature probably 

 accounts for the failures of early investigators to obtain active 

 extracts. 



Action of the cestr ns-i}ihihiting hormone. The ovaries of 

 animals in which oestrus has been inhibited are described by 

 Papanicolaou (487) as showing complete absence of corpora 

 lutea, and the presence of a large number of medium-sized 

 follicles, in which the theca interna was enlarging preparatory 

 to atresia. The action of the hormone on the ovary and uterus 

 has been studied by Hisaw and co-workers (305) and Gley (244). 

 The former state that a condition analogous to that found 

 during pseudo-pregnancy is set up in the uterus. Gley, on the 

 other hand, describes effects similar to those following ovariec- 

 tomy. This result, however, is highly improbable if a true 

 corpus luteum effect is being reproduced. 



Assay of the cestr us-inhihiting hormone. Papanicolaou (487) 

 suggested that the oestrus-inhibiting hormone should be assayed 

 by its power to inhibit oestrus in the guinea-pig for a period of 

 five days, one unit being the amount required to do this. Such a 

 method, however, would clearly be both inaccurate and cumber- 

 some. Since it is not possible to say precisely when the next 

 oestrous period of an animal is due, the degree of inhibition of this 

 period cannot be gauged precisely. Hisaw (304) and his co- 

 workers assay their extract by its ability to relax the pubic 



