THE CYCLIC CHANGES IN THE MAMMALIAN OVARY. 



By LEO LOEB. 



{Read April 23. igii.) 



The observations which I wish to report to you are of interest 

 from several points of view : 



1. The process upon which the sexual cycle in mammals depend 

 has been analyzed, and a regulatory mechanism was found to exist 

 within the ovary. 



2. A striking illustration is presented of the fact that the struc- 

 ture of organs is in many instances at least not a definite one, but 

 varies in correspondence with the functional condition of the organ. 



3. The accurate description of the normal cyclic changes in the 

 mammalian ovary serves as a basis for the investigation of the patho- 

 logical deviations which interfere with the natural course of the 

 sexual functions and may lead to a temporary or lasting sterility. 



4. We found in the ovary structures which must in all probability 

 be interpreted as early stages of embryos developing spontaneously 

 parthenogenetically within the ovary and it is probable that the devel- 

 opment of these parthenogenetic embryos is related to certain phases 

 of the sexual cycle. 



In the ovary of the guinea-pig definite and very interesting cyclic 

 changes exist which I made the object of my studies in the last few 

 years. 



The mammalian ovary consists of two principal constituent parts, 

 namelv : First, large and small bodies lined by granulosa cells and 

 filled wath fluid, the so-called follicles ; and, secondly, the corpora 

 lutea. Both follicles and corpora lutca have only a brief existence; 

 thev develop to a certain point and then they degenerate and grad- 

 uallv disappear. The follicles contain the ova. At certain periods 

 of the sexual cvcle a few follicles that have reached maturity rupture. 

 The ova reach the Fallopian tubes and uterus and after fertilization 



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