698 OF REPRODUCTION. 



Plate I.) The Ovum then begins to move towards the periphery of the 

 Graafian follicle; and always towards that point of it which is nearest the 

 surface of the Ovary. This movement appears to be due, in the first instance, 

 to the 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 

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

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

 thickened. 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 con- 

 tents 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 Graafian follicle, into the funnel-shaped entrance of the Fallopian tube, 

 the Retinacula 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 some- 

 times known it to be subsequently expelled from the ovary ; but it appears 

 more commonly to coalesce with the surrounding envelope, and to constitute, 

 together with it, the lining of the cavity, which is usually found in the Corpus 

 Luteum. The substance 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. 



913. The term Corpus Luteum has been usually applied to a reddish-yel- 

 low substance, glandular in aspect, friable in consistence, and very vascular; 

 which occupies the part of the Ovary from which the germ has escaped, and 

 is larger or smaller according to the length of time that has elapsed since con- 

 ception. At first it is usually so large as to occasion a considerable projection 

 on the surface of the Ovary ; its form is oval, or resembles 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 

 Luteum may be distinguished from substances, bearing a general resemblance 

 to it, but very different in their character. The following is Dr. Mont- 

 gomery's account of it. " Its centre exhibits either a cavity, or a radiated 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 

 proceeds, the opposite parts of this cyst approximate, and at length close to- 

 gether, 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 stelliform. 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 stimu- 

 late it. After Delivery, the size of the Corpus Luteum rapidly diminishes; 



* Signs of Pregnancy, p. 226. 





