324 INTERNAL SECRETIONS 



an extract from that ovary of the pregnant cow which contains 

 no corpus luteum, but in which the interstitial tissue is highly 

 developed during pregnancy. The extract showed a very 

 marked effect on the uterus. Since such an ovary differs from 

 the ovary of a non-pregnant cow^ only in the fact that the 

 interstitial tissue is hypertrophied, Fellner is inclined to 

 adopt the view that the interstitial cells of the ovary of the 

 pregnant animal secrete the same substance as the corpus 

 luteum. Fellner even suggests that the action of the inter- 

 stitial cells of the ovary during pregnancy is quantitatively 

 similar to that of the corpus luteum. When comparing the 

 intensity of the effect of an extract prepared from the corpus 

 luteum excised from the ovary with that of an extract pre- 

 pared from the whole lutein-containing ovary of the pregnant 

 animal, Fellner found that the intensity in the second case 

 was greater than in the first. He explains this result by as- 

 suming that in the second case the effect was produced by the 

 combined action of the lipoids extracted from the corpus 

 luteum together with the lipoids of the interstitial cells, 

 whereas in the first case only the lipoids of the corpus luteum 

 were present in the extract. Finally Fellner states that an 

 extract of a corpus luteum of a non-pregnant animal has 

 quantitatively the same effect as that of a corpus luteum 

 of a pregnant animal. The result of these experiments of 

 Fellner may be explained also by the fact that there is in the 

 ovary during pregnancy an intensified development and 

 atresia of follicles, from which interstitial cells are formed. 

 As we have seen in Chapter V., this explanation is in reality 

 identical with Fellner 's. 



In all the above-mentioned experiments the augmentation 

 of the uterus was made use of as a quantitative test of the 

 hormonic effect of a given extract. By the same method 

 Fellner arrived at the conclusion that the extract of a placenta 

 is equivalent to that of an extract of forty corpora lutea. 

 There were never any changes in the kidneys. Though there 

 was a great hypertrophy of the mammary gland, milk secretion 

 was never observed. 



Herrmann (1915) investigated the effects of extracts pre- 

 pared by ether. He made a comparative study of extracts of 

 corpora lutea excised from ovaries, of extracts of ovaries 

 without corpora lutea and of extracts of the placenta. By 



