86 BENJAMIN H. WILLIER 



than one egg is present. Such primary follicles are enclosed by 

 a thickened wall of connective-tissue fibers, which is not unlike 

 the wall of the male sexual cords. Magnusson ('18) described 

 large vesicle-like structures which in six different cases appeared 

 to resemble Graafian follicles, but in none did he find germ ceUs. 



The interstitial cells are of two types, those which resemble 

 the interstitial cells of the normal testis and of other free-martin 

 gonads and those which resemble lutein cells of the corpora 

 lutea in cattle. The latter are of large size, and the cytoplasm 

 is filled with large granules staining yellow with Mallory's 'triple 

 stain.' These lutein-like cells usually occur in locahzed masses 

 distributed chiefly at the periphery of the sex-cord region. One 

 of these masses is a large, rounded collection enclosed by a con- 

 nective-tissue capsule, which measures 1 mm. in diameter, and 

 resembles closely a miniature corpus luteum. Magnusson ('18) 

 described three gonads in which similar bodies of lutein-like, 

 cells were found. He found even larger bodies, as he states on 

 page 47, ^' ... einen verhaltnismassig grossen intensiv 

 gelben Korper von 3 mm. Durchmesser ein, der von einer fibrosen 

 Kapsel umgeben war." The origin of these lutein-like cells 

 cannot be decided from the meager evidence furnished by this one 

 case, but it is not improbable that they arise from the follicular 

 (granulosa) cells of atretic follicles. 



The occurrence of primary follicles in the sex-cord region raises 

 the question of their origin. There are two possible explana- 

 tions of their occurrence. In the first place, a few of the cords of 

 Pfliiger may have invaginated before the optimum conditions 

 for the action of the male sex hormones were established. This 

 view is supported by the peripheral position of the majority of 

 the primary follicles and masses of lutein cells, which probably 

 arise from the follicles. Secondly, such folHcles may have 

 arisen from the 'medullary foUicles' of the ovary. The evidence 

 is good for this point of view, since the sex-cord region is com- 

 paratively small, and it ought to be larger if any of the cords of 

 Pfliiger had invaginated. Allen ('04) and others have described 

 simple follicles containing germ cells in the medullary cords of 

 foetal ovaries. Such follicles with germ cells are also present in 



