178 INTERNAL SECRETIONS OF THE OVARY 



The expulsion of such abnormally long-lived corpora lutea usually 

 brings about the return of cestrus. In the same way the human 

 cycle may cease when the corpora lutea persist abnormally and 

 the removal of such abnormal corpora lutea is followed, accord- 

 ing to Ochsnier (482), by the return of the cycle. Quite recently 

 it has been found possible to prolong the functional life of 

 ovarian luteal tissue almost indefinitely by the injection of 

 sodium hydroxide extracts of the anterior pituitary body. Thus, 

 in the mouse and rat the immense production of luteal tissue 

 which follows such treatment is associated with the complete 

 absence of oestrus and ovulation, while in the X-rayed animal 

 the luteinization of the tissue of the sterilized ovary by similar 

 treatment also brings about the suppression of oestrus. 



Mechanism of cestrus inhibition. Definite information is 

 lacking as to how the corpus luteum brings about the suppression 

 of oestrus. It is clear that it cannot be merely a local mechanical 

 effect in the ovary itself ; the presence of a corpus luteum 

 in one ovary is sufficient to inhibit the oestrus-producing 

 activity of both ovaries. In the cow and other usually mono- 

 tocous animals only one corpus luteum at a time is normally 

 present. In polytocous animals, the same condition can be 

 produced experimentally by eliminating the Graafian follicles, 

 and hence the corpora lutea, of one ovary by exposure to X-rays. 



Preparation of a-strus-inhibiting extracts. By analogy with 

 other ovarian functions, it is probable that the oestrus-inhibiting 

 action of the persistent corpus luteum is brought about by some 

 endocrine activity. Only very recently, however, have extracts 

 been prepared from the corpus luteum which have any genuine 

 oestrus-inhibiting activity. Corner and Hurni (129) reported 

 negative results from the injection of rats with corpus luteum 

 preparations, while Loeb (400) working on the guinea-pig, was 

 unable to produce regularly positive eftects. Pearl and Surface 

 (512) claim to have succeeded in stopping ovulation in laying 

 hens by injection of extracts of a commercial preparation of 

 corpora lutea, while Kennedy (320) reported positive results on 

 the rabbit by the injection of sahne extracts of similar material. 

 Pearl and Surface, however, state that toxic effects were 

 produced by their extracts and the same appears probable in 

 Kennedy's experiments from the fact that ovulation was 



