EXPERIMENTAL PRODUCTION OF HYPOTYPICAL OVARIES. I 15 



persists at least for some time after the resumption of feeding. 

 Further investigations will have to solve this problem. Our 

 results may perhaps also have some bearing on the condition 

 of the ovaries during pregnancy. We have shown that in guinea 

 pigs ovulation does not occur during pregnancy unless the 

 corpora lutea have been extirpated. In other species however, 

 and especially in man it seems that during pregnancy a matura- 

 tion of the follicles is lacking. Our experiments suggest that 

 this may depend upon a relative insufficiency of food available 

 for the ovaries during pregnancy; thus an approach to a hypo- 

 typical condition of the ovaries would be produced. 



SUMMARY. 



Underfeeding, if very pronounced, prevents maturation of the 

 follicles in the ovaries of the guinea pigs in all cases and in the 

 large majority of cases leads to the production of hype-typical 

 ovaries in which atresia of follicles sets in before the follicles 

 have reached medium size. Underfeeding leads to a premature 

 solution of granulosa cells. Connective tissue is more resistant to 

 lack of food than the granulosa. The uterus in cases of under- 

 feeding is in a resting or atrophic condition. Thus underfeeding 

 produces at least temporary sterility. Those cells farthest 

 removed from the blood vessels suffer first as the result of under- 

 feeding, die and become dissolved, while in those granulosa cells 

 which remain alive the growth stimulus which in part at least 

 emanates from the ovum causes for a short time a normal cell 

 proliferation. Just as the underfeeding produces more pro- 

 nounced general effects in younger animals, the effect on the 

 ovaries is likewise more marked in younger animals. Through 

 underfeeding it is, however, possible to produce a hypotypical 

 condition even in old guinea pigs. In those animals which had 

 been pregnant at the beginning of the experiment underfeeding 

 led to abortion. 



There exists a noteworthy analogy in the relation of cell 

 proliferation to cell destruction in the hypotypical ovaries and 

 in stationary or retrogressing tumors. 



Our results emphasize the distinction between food stuffs 

 and proliferative cell stimuli and they may in addition throw 

 light on the condition of the ovaries during pregnancy. 



