The Menstruation and Ovulation of Macacus rhesus. 205 



Hypertrophy now takes place, the wall becomes much thickened 

 and folded, and a growth of cells takes place from the wall into the 

 cavity of the follicle, the sharply marked boundary of the wall is lost, 

 and the long protoplasmic processes of the cells within the cavity are 

 continuous with the cells of the wall. 



The vessels of the wall now become enlarged and increased in 

 number. Hypertrophy is no longer evident ; the tissue is denser and 

 shrunken, and the whole structure is reduced in size. Gradually the 

 cavity of the follicle is also reduced in size, and the tissue contained 

 therein becomes denser until it is hardly to be distinguished from 

 that composing the wall. * 



Finally the whole of the cellular remains of the follicle consist of a 

 comparatively small mass of cells with no trace of the follicle wall 

 and no central cavity, a nearly solid mass of tissue, in the midst of 

 which a few blood vessels run. The cells which compose this mass 

 now scarcely differ from the ovarian stroma cells ; they have gradu- 

 ally undergone the change, and instead of branched cells they now 

 appear as polyhedral cells or multinucleated polyhedral protoplasmic 

 masses with intermediate finely branched connective tissue elements 

 bounding them. 



This structure is surrounded by a layer of fine nucleated fibres ; 

 but soon these disappear, and the remains of the follicle are no longer 

 distinguishable from the rest of the ovarian stroma. 



Throughout, no trace of a blood clot within the follicle was seen, 

 and therein these ruptured follicles differ from what is usually de- 

 scribed as a normal ruptured follicle in the human female. This 

 difference between two animals, both of which undergo menstruation, 

 is remarkable and worthy of special attention. 



I have some reason to believe the difference may be due to the 

 presence or absence of the breeding season in monkeys, and to 

 periods in the human female, which are in the one case favourable, 

 and in the other case not favourable, to conception. 



If this be true, the period of the human female which is unfavour- 

 able to conception would be comparable to the non-breeding season of 

 monkeys, and the period favourable to conception with the breeding 

 season of monkeys. 



It is not maintained that among civilised peoples at the present 

 day there are definite breeding and non-breeding times, but the com- 

 parison is in harmony with the view that at one period of its exist- 

 ence the human species had a special breeding season. 





VOL. LX. 



