362 B. F. KINGSBURY 



In connection with the comparison of the structures within the 

 ovary to the testis tubules just considered, it may be said at this 

 point that the cells are as strikingly follicle cells at this stage and 

 place as subsequently in the development of the follicles of the ado- 

 lescent and adult periods. This is particularly clearly shown in a 

 comparison of such cells when a mitochondrial technique has been 

 employed. The disposition of the mitochondrial granules in the 

 inner ends of the cells in each instance serves to make the agree- 

 ment more striking. The fact that these so-called medullary 

 cords develop into follicles should leave no doubt of their ovarian 

 character. 



The medullary follicles. The development of the follicles with- 

 in the medulla of the ovary of the kitten has been studied in de- 

 tail by von Winiwarter and Sainmont, who apply the name of 

 'medullary follicles' and regard their appearance as marking a 

 third stage in the development of the ovary. Their description, 

 briefly stated, is as follows : At eight days postpartum the med- 

 ullary cords are markedly elongated; at sixteen days they have 

 increased in volume and the cells have hypertrophied and be- 

 come more columnar in shape. This stage is the last one in which 

 a connection of the medullary cords with Pfliiger's egg cords 

 exists. 0\iiles exist within the medullary cords, generally smaller 

 than those of the primitive cortex. Small medullary cords are 

 described in the zone bounding the primitive cortex and contain- 

 ing o\ailes which belong to Pfliiger's egg cords. Such they inter- 

 pret as ovules of Pfliiger's egg cords which have become isolated 

 with a medullary cord. At twenty-three days p.p., primordial 

 medullary follicles, both uni- and pluri-o\ailar, are beginning 

 their development. At thirty-five days, the next described 

 stage, the medullary follicles have become voluminous struc- 

 tures. These they group as follicles in process of growth and folli- 

 cles fully formed, the latter possessing an antrum comparable to 

 the antrum of the definitive Graafian follicles of the adult period. 

 The medullary follicles now undergo a peculiar degeneration dur- 

 ing the next two or three weeks, so that, at sixty to sixty-five 

 days p.p., all remains of the medullary follicles have completely 

 disappeared, this degeneration being accomplished or accompa- 



