596 OF REPRODUCTION. 



shortening of the Retinacula in that direction ; and whilst the Ovum lies 

 against the membrane of the Ovisac, a gradual thinning of the latter seems to 

 take place. At the same time an important change is occurring in the outer 

 wall of the Graafian follicle, especially at the part most deeply imbedded in 

 the Ovary ; its vascularity is greatly-increased, and its substance appears thick- 

 ened. This thickening is probably due to the deposition of blood in a state 

 ready to become more highly organized, upon the exterior of the Ovisac ; and 

 the consequence of it is, that considerable pressure is made upon the contents of 

 the follicle, the effect of which is, of course, exerted most upon the thinnest 

 part of it. Thus, a sort of vis a tergo is exercised against the Ovum and the 

 Disc (consisting of the tunica granulosa and the central part of the retinacula) 

 in which it is imbedded ; and the whole is forced, by the rupture of the Graa- 

 fian follicle, into the funnel-shaped entrance of the Fallopian tube, the Re- 

 tinacula being gradually detached from the Membrana Granulosa, which is 

 left behind. This action is represented in Fig. 8, Plate I. What becomes of 

 the Ovisac is not certain. Dr. Barry affirms that he has sometimes known it 

 to be subsequently expelled from the ovary ; but it appears more commonly to 

 coalesce with the surrounding envelop, and to constitute, together with.it, the 

 lining of the cavity, which is usually found in the Corpus Luteum. The sub- 

 stance known under this name is found in the Ovary, after the Ovum has 

 escaped from it ; and the importance of the question, how far its presence may 

 be regarded as an indication that Conception has taken place, requires that we 

 should have clear ideas respecting its nature. The term Corpus Luteum has 

 been usually applied to a reddish-yellow substance, glandular in aspect, friable 

 in consistence, and very vascular ; which occupies a larger or smaller part of 

 the Ovary, from which the germ has escaped, according to the length of time 

 that has elapsed since conception. At first it is usually so large, as to occasion 

 a considerable projection on the surface of the Ovary ; its form is oval, or resem- 

 bles that of a bean. When cut across, its dimensions are usually found to be 

 from 4 to 5-8ths of an inch in its long diameter, and from 3 to 4-8ths in its 

 short ; and it thus occupies from a fourth to a half of the whole area of the 

 ovarium; but these dimensions are not unfrequently exceeded. The centre 

 of this substance is hollow ; and by a proper acquaintance with this character, 

 the true Corpus Lujeum may be distinguished from substances bearing a gene- 

 ral resemblance to it, but very different in their character. The following is 

 Dr. Montgomery's account of it. "Its centre exhibits either a cavity or a radi- 

 ated or branching white line, according to the period at which the examination 

 is made. If within the first three or four months after conception, we shall, I 

 believe, always find the cavity still existing, and of such a size as to be capable 

 of containing a grain of wheat at least, and very often of much greater dimen- 

 sions ; this cavity is surrounded by a strong white cyst ; and as gestation pro- 

 ceeds, the opposite parts of this cyst approximate, and at length close together, 

 by which the cavity is completely obliterated, and in its place there remains an 

 irregular white line, whose form is best expressed by calling it radiated or stel- 

 liform. This is visible as long as any distinct trace of the Corpus Luteum 

 remains."* The true Corpus Luteum is further distinguished by its capability 

 of being injected from the vessels of the Ovary ; which is not the case with 

 Tubercular deposits, or other substances which may simulate it. After Deli- 

 very, the size of the Corpus Luteum rapidly diminishes; and in a few months 

 it ceases to be recognizable as such. The cicatrix by which the Ovum has 

 escaped is visible for some time longer ; but this, too, according to the careful 

 researches of Dr. Montgomery, cannot be distinguished at a subsequent period. 

 Hence there is no correspondence between the number of Corpora Lu tea found 



* Signs of Pregnancy, p. 226. 



