FORMATION OF TI1E CORPUS LUTEUM. 897 



this gradually diminishes, partly in consequence of the increased growth of 

 the yellow substance, and partly owing to the general contraction of the 

 ovisac, until it is at last nearly obliterated or reduced to a sort of stellate 

 cicatrix (> A). An effusion of blood usually takes place into this cavity, 

 in the Human female, at the time of the rupture of the ovisac; but the co- 

 agulum which is left, takes no share in the formation of the yellow body. 

 It generally loses its coloring matter, and acquires the characters of a fibrin- 

 ous clot ; and this may either form a sort of membranous sac lining the 

 cavity, or it may become a solid mass occupying the centre of the stellate 

 cicatrix. 1 



745. The later part of the history of the Corpus Luteum is greatly in- 

 fluenced by the impregnation or non-impregnation of the Ovum whose extru- 

 sion it has followed. If conception do not take place, the corpus luteura 

 seldom attains a size greater than that of a small pea, and is very commonly 

 less than this ; and it begins to diminish about the time of the next menstrua- 

 tion, its shape, which was at first globular, becoming somewhat collapsed 

 and flattened. This diminution is due in the first instance to the absorption 

 of part of its contained coagulum, which usually at the same time loses part 

 of its coloring matter ; but contemporaneously with this, there is an increase 

 in the proper yellow substance, which also becomes brighter in color from 

 the presence of a large quantity of oleaginous matter in its cells. Soon, 

 however, the yellow substance becomes softer and more friable, showing less 

 distinctly the markings of its convolutions ; whilst at the same time it be- 

 comes more intimately connected with the neighboring tissues. The central 

 coagulum becomes a faint, whitish, stellate cicatrix ; and the yellow sub- 

 stance assumes various irregularities of form, and gradually decreases in size. 

 As a general rule, the corpus luteum of the non-pregnant female is reduced 

 within six or eight weeks to a very insignificant size ; but it may then remain 

 almost unchanged for many mouths ; so that, in the ovaries of females who 

 have menstruated regularly, numerous obsolete corpora lutea may be dis- 

 tinguished. But if, on the other hand, the discharged ovum should be fer- 

 tilized, and pregnancy should supervene, the corpus luteum instead of reach- 

 ing its maximum of development in three or four weeks, and then undergoing 

 atrophy, continues to develop itself for a considerable period, and does not, 

 in fact, become very decidedly retrograde, until after the termination of ges- 

 tation. This difference relates not only to its size, but also to its aspect and 

 general characters. Its size appears to be usually greatest between the third 

 and the sixth months of pregnancy ; it retains its globular or only slightly- 

 flattened form ; and it continues to give to the touch a sense of considerable 

 resistance and solidity. The convoluted wall of yellow substance becomes 

 much thicker in proportion to the space in its interior ; so that whilst in the 

 non-impregnated female its thickness never exceeds one-eighth of an inch, 

 and is usually much less, that of the pregnant female measures as much as 

 from three-sixteenths to one-fourth of an inch. This substance, moreover, 

 acquires a firmer and" more highly organized structure; but instead of pre- 

 senting an increased brightness of color, it fades to a dusky and indefinite 

 hue. As, from the time that impregnation takes place, the periodical activity 

 of the ovary is suspended, no new vesicles protrude themselves from its sur- 

 face until after the completion of gestation ; and even those which, at the 

 date of conception, happened to be more or less prominent, appear again to 

 recede. Hence, if the period of pregnancy be at all advanced, the corpus 

 luteum is not found, like that of menstruation, in company with unruptured 

 vesicles in active process of development. After parturition, the corpus 



1 This process was first accurately described by M. Pouchet, in his Theone Positive 

 de rOvulation Spontanee, 1847. 



