THE FUNCTION OF (ESTRIN 131 



able, is negligible compared with that found during pregnancy or 

 pseudo-pregnancy. In this animal, however, the growth from 

 prooestrus to the end of pseudo-pregnancy does appear to be 

 continuous. Hartman's results show that injection of folli- 

 cular extract into the ovariectomized opossum produces growth 

 only equal to that of oestrus. In the rabbit the distinction be- 

 tween the oestrous proliferation of the mammary gland and 

 that occurring under the influence of the corpus luteum is most 

 obvious. Ancel and Bouin (34) and Mntemberger (624) 

 distinguish very definitely between the slight mammary pro- 

 liferation characteristic of cestrus, which can be produced by the 

 injection of oestrin, and the extensive hypertrophy which is 

 characteristic of pregnancy and pseudo-pregnancy. The latter 

 phase of growth does not occur during even the most prolonged 

 oestrus and cannot be caused by the injection of the oestrus- 

 producing hormone. Fellner's (192) extensive illustrations of 

 the effects of his ovarian extracts on the mammary gland 

 make it perfectly obvious that in no case was greater develop- 

 ment induced than is normally found at oestrus. 



The comparative influence of oestrin on the mammae of the 

 rat and guinea-pig is also instructive. In the former animal the 

 growth produced by oestrin is negligible (565) while in the latter 

 it is considerable (230). This comparison corresponds exactly 

 with the conditions in the normal animals at oestrus. 



The evidence that oestrin can cause complete development of 

 the mammary gland is therefore quite inconclusive. Probably, 

 at most, an exaggeration of the proliferation characteristic of 

 oestrus can be produced. 



(/) SIGNIFICANCE OF DISTRIBUTION 



The occurrence of oestrin-like substances in the male cannot 

 be discussed until their identity with oestrin is demonstrated. 

 As regards the non-pregnant female, the distribution of oestrin 

 presents few problems. Its presence in the follicles and stromal 

 tissue of the ovary, its very doubtful presence in the corpus 

 luteum, and the small and varying quantities in the blood and 

 urine, are quite in accordance with expectation. 



Significance of occurrence in body fluids during pregnancy. 



