i8o INTERNAL SECRETIONS OF THE OVARY 



to be injected to produce positive results, but control injections 

 showed that the administration of even larger amounts of inert 

 fat emulsions had no effect on the cycle. 



Beginning work from another viewpoint Hisaw (303) was able 

 to prepare extracts of corpus luteum which had the remarkable 

 property of dissolving the pubic ligaments of the guinea-pig and 

 the pocket gopher. This extract was afterwards found to have 

 other properties characteristic of luteal activity. Thus, its 

 injection into the normal animal inhibited oestrus and produced 

 the sensitivity of the uterus to mechanical stimulation. The 

 improvement of the extraction of the active substance from the 

 corpus luteum is still being carried on by Hisaw and his 

 co-workers, but the most recent information shows that their 

 extract is prepared essentially as follows. The corpora lutea of 

 the sow are used, preferably those of a pregnant animal. The 

 solid tissue only is employed and after grinding in a mortar, 

 twice the volume of acidified ethyl alcohol is added (98 c.c. of 95 % 

 alcohol — 2 c.c. of HCl). The mixture is shaken thoroughly and 

 allowed to stand for twelve hours. The alcohol is then decanted 

 and a second extract made. This second extract is removed by 

 means of a press and combined with the first extract. The 

 alcoholic extract may be used as a stock solution and keeps 

 well. In the further stages of purification, the alcohol is filtered 

 and evaporated in a vacuum at a low temperature. The aqueous 

 residue after removing the alcohol is neutralized to a pH. of 5-4 

 with a 15% solution of NaOH. A heavy precipitate is formed 

 which should be filtered off and re-extracted. The salts pre- 

 sent may be removed by dialysis. 



Gley (243) has described the preparation of an oestrus- 

 inhibiting extract by the following method. Corpora lutea of 

 the cow are extracted with tartaric acid and the extract treated 

 with lead acetate. This brings down various toxic substances, 

 but not the hormone, which is water-soluble. Further purifica- 

 tion is effected with Cu(0H)2, which is subsequently removed 

 by HgS. After neutralization the solution is protein free and may 

 be injected. It causes congestion of the uterus and suppression 

 of oestrus. Payne, Peenan, and Cartland (511) have described 

 the preparation of an oestrus-inhibiting substance from corpora 

 lutea by saponification. 



