AX ATOMY AXD HISTOLOGY OF THE OV ARIES 547 



the hen-feathered sebrights which are absent in cock-feathered breeds, and 

 which are apparently identical with the lutein cells occurring in the ovary 

 of the female birds. The lack of development of the male plumage' in 

 females may, therefore, be attributed to the secretion produced by these 

 cells. 



Conditions in Mammals. In mammals, on the other hand, structural 

 changes in the corpus luteum are definitely associated with the func- 

 tions of pregnancy and menstruation, which are of course not distinctly 

 represented in birds. It would appear, therefore, that our informa- 

 tion is at fault, or else that we have an interesting instance of similar 

 organs exhibiting totally different properties in the phylogenetic series. 



Histology 



The structure of the cells of the corpus luteum varies considerably in 

 different stages in its development. When it attains its maximum size, 

 and is presumably most active physiologically, they present the appearance 

 in ordinary preparations illustrated in Fig. 6. 



Cytology. We know next to nothing of the finer cytology, much less 

 of secretory changes in the human species, owing to the impossibility of 

 securing properly seriated stages. This difficulty is being overcome in 

 laboratory animals through the introduction of new methods of technic. 

 For instance, Corner and Hurni are applying Evans' method of vital stain- 

 ing, by which all the corpora lutea existing at the time of application are 

 colored, while those arising subsequently remain unstained ; and Stockard 

 and Papanicolaou (c) are able to predict, through the inspection of the 

 uterus and the vagina of guinea pigs, the existence of all the different 

 phases in the developmental cycle of the corpora lutea in the ovary. 



Cell Inclusions. As might be expected, the cells contain mitochondria, 

 which may easily be stained in the living condition with janus green; they 

 contain as well a definite reticular material, evident only after special 

 methods of fixation and staining, and the characteristic neutral fat, lipoid, 

 and pigment. The best account of the cytology of the corpora lutea is 

 given by Corner (e). 



Secretory Phenomena. Working with the bat, Van der Stricht has 

 succeeded in tracing the histological changes involved in the production of 

 two types of secretion, a serous and a lipoid. The serous secretion re- 

 sembles the liquor folliculi and is formed, after the rupture of the follicle, 

 by the young lutein cells. Van der Stricht observed its elaboration in the 

 form of tiny droplets within the cells, its discharge into the intercellular 

 spaces, and passage into the lymphatics, as indicated in Fig. 4. This 

 secretion increases in amount during the segmentation of the ovum into 

 two or three bastomeres, decreases later, and finally disappears completely 



