io6 INTERNAL SECRETIONS OF THE OVARY 



Table 6. — Weight of the Unit of CEstrin. 



(continued). 



found in the amounts required. Pratt and Allen (519) indeed 

 claim to have produced clinical effects with very small doses. 

 The purity of an extract may best be stated in terms of the 

 weight of the unit. The weights given by various authors are 

 collected in Table 6. Such figures, of course, can be only ap- 

 proximate. The variety of techniques used for assay, and 

 unavoidable inaccuracies, make strict comparison impossible. 



(/) DISTRIBUTION 



Extracts were originally made only from animal tissues, 

 but recently the presence of the oestrus-producing hormone has 

 been detected in body fluids. In addition, oestrin or oestrin-hke 

 substances have been obtained from various plant sources. 



Distribution m the ovary. The ovarian follicle was originally 

 used for extraction of the hormone and has long been considered 

 its essential site of origin. Allen and his co-workers (24) by 

 the use of centrifuged and filtered material showed that oestrin 

 is actually present in the liquor folliculi and not merely in the 

 cellular contents which are aspirated at the same time. Zondek 

 and Aschheim (650) claim to have shown by their implantation 

 method (see p. 91) that the hormone is present in the theca 



