434 REPRODUCTION AND DEVELOPMENT 



the drained cavity of the follicle, whose walls, especially the stratum 

 granulosum, remain. These latter cells degenerate and the internal 

 layer beneath them by proliferation soon gives rise to a cellular mass 

 sufficient to fill the now restored sphere of the follicle. Trabeculse of 

 fibrous tissue, containing an abundance of blood-vessels, soon divide 

 the little body into lobules. The cells composing this new mass are 

 colored yellow by lutein, a lipochrome of unknown composition which 

 gives the blood-serum its faint yellowness. 



In case the liberated ovum be not fertilized, in about three weeks the 

 yellow cells become more and more white like connective-tissue of a 

 special cicatricial sort, and in course of time, this, now called the corpus 

 albicans, almost disappears. If we suppose, as many at present do, that 

 ovulation takes place normally about a fortnight before menstruation, 



FIG. 248 



Section in the ovary of a cat: 1, free peritoneal border of the ovary; l', attached border; 

 2, central stroma, fibrous and vascular in its structure; 3, peripheral stroma containing unstri- 

 ated muscle-fibers; 4, blood-vessels; 5, Graafian follicles in the earliest stage (about 36,000 in 

 number altogether); 6, 7, 8, more advanced and larger follicles embedded more deeply; 9, an 

 almost mature follicle containing a conspicuous ovum; 9', a follicle which has accidentally lost 

 its ovum; 10, a corpus luteum. 8 /i- (Schron.) 



it is clear that the contents of the corpus luteum might well enough influ- 

 ence the changes, constructive and then destructive, which occur in the 

 uterus previous to the outward flow of uterine debris. The sexual appa- 

 ratus is constructed and acts, however, on the supposition of continually 

 repeated conception and pregnancy, and yet in the above manner it pro- 

 vides for disappointment. 



If, however, the ovum be fertilized within a week or so after ovulation 

 (the ovum will persist at least as long as this), the. corpus luteum vera, as 

 it is then called, becomes more fully developed and larger. More than 

 this, it persists in its entirety until after parturition, when it degenerates 

 in practically the same way as does the corpus albicans. On this hypoth- 

 esis, then, the hollow sphere from which an ovum has escaped becomes 

 forthwith filled with epithelium which provides a stimulant for such 

 temporary development of the organism as is required for the growth 



