558 



UTERUS AND ITS APPENDAGES. 



folliculi, retaining its ordinary condition. 

 Already a slightly wavy outline is perceptible 

 in the follicle (fig. 381.), which is due to the 

 growth of the inner membrane having con- 

 tinued after the outer coat has ceased to ex- 

 pand. 



The inner coat of the follicle, when it has 

 thus acquired a yellow colour, is seen, by the 

 aid of the microscope, to have undergone an 

 important and yet very simple change. On 

 its inner surface, or that which is turned 

 towards the cavity of the ovisac, it presents 

 the appearance of a transparent and nearly 

 structureless membrane, in the substance of 

 which are imbedded numerous oil droplets, 

 very minute, and aggregated in little masses, 



Fig. 382. 



Cells filled with oil-granules which give the yellow 

 colour to the inner coat of the Graafian follicle be- 

 fore it has burst, forming the substance termed cor- 

 pus luteum. (Ad Nat. x 350.) 



a, separate cells ; b, the same imbedded in the 

 structureless membrane. (From the same subject 

 asfiffs. 380. and 381.) 



with a certain regularity which suggests the 

 idea that they have either been originally 

 deposited around a centre globule, or are 

 contained in cells or vesicles, the cell-wall 

 of which is not very discernible (fig. 382. 

 b}.^ Deeper towards the outer surface of the 

 ovisac the oil droplets or granules become so 

 numerous as to prevent the recognition of any 

 other structure until the greater portion of the 

 oil has been dissolved out by macerating the 

 part in ether. If, after this process, the tissue 

 which remains be washed in spirit or water, 

 and subsequently treated by acetic acid, it is 

 seen to be composed of numerous blood- 

 vessels, and of developed as well as embryonic 

 fibres of connective tissue, which latter, how- 

 ever, are only faintly indicated, and are con- 

 nected together by a transparent membrane. 

 The proportion of developed fibres of con- 

 nective tissue is here very large, whilst in 

 less advanced follicles the embryonic fibres 

 preponderate (fig. 375.). 



Another and perhaps more satisfactory 

 mode of examining the yellow coat of the 

 Graafian follicle in this stage, consists in slow 

 maceration in a very weak preservative fluid 

 (glycerine and water). The cells, which this 

 coat contains in great abundance, can now be 

 obtained separately for observation. They 

 are seen to consist of a transparent cell-wall, 

 filled with oil granules (fig. 382. a). The 

 average cells vary in diameter from -$%$" to 

 2o\ro"> Dut many are smaller, and others lar- 

 ger. Occasionally a cell may be seen to have 

 burst, its contents having escaped ; a few oil 

 granules, however, may still be perceived ad- 

 hering to the cell-wall, the torn margins of 

 which are very readily defined. There can be 

 no doubt that these cells are the "peculiar 



granules" so frequently described and figured 

 by Barry in his account of the various con- 

 ditions and stages of development of the 



ovisac. 



The colour of the yellow coat the so-called 

 carpus luteum is not alike in all animals. 

 In some of the Mammalia it is of a bright 

 orange ; in others it inclines to red. In Man, 

 as already stated, the inner surface of the 

 follicle, when ripe, is occasionally so loaded 

 with bright red capillaries that the usual 

 appearance is obscured, but its ordinary as- 

 pect presents the clear chrome yellow just 

 described. That this yellow colour, like that 

 of the yolk of the bird's egg, is due to the 

 presence of the oil globules (fig. 382. b) which 

 everywhere penetrate the tissues of this coat, 

 is rendered sufficiently apparent : first, by the 

 fact that treatment by ether, which dissolves 

 out the oil granules, leaves the remaining 

 membrane nearly white ; and secondly, that 

 maceration in water has, to a certain ex- 

 tent, the like effect, but in this case arising 

 from the maceration, causing the animal 

 membrane to swell and become opaque, thus 

 obscuring its previous transparency, and ren- 

 dering the oily portions only faintly dis- 

 cernible through it, as judged by the naked 

 eye, though they are still readily discoverable 

 under the microscope. 



Third Stage. Period of Rupture or Dehis- 

 cence of the Follicle, and Escape of the Ovum. 

 This is termed by Pouchet the period of 

 parturition, in which, after the preparatory 

 changes already described, the ovum quits 

 the Graafian follicle in order to enter the 

 Fallopian tube. It is therefore for the ovisac 

 what the process of parturition is for the 

 uterus, viz., the act by which the ovum, after 

 being matured to a certain point of perfection, 

 is expelled from its cavity. 



The process by which the dehiscence of the 

 follicle is effected in Mammalia is in some re- 

 spects different from that which causes the 

 expulsion of the ovum, from its containing 

 capsule, in the vertebrata below them. In 

 birds, reptiles, and fishes, and, indeed, in 

 the Invertebrata generally, the ovum is of so 

 large a size in comparison with the ovicap- 

 sule, that the simple increase of the former, 

 as the time of theovipont* approaches, is suffi- 

 cient to cause the bursting of the sac at the 

 point where the coats have been prepared for 

 rupture by previous attenuation. But in the 

 Mammalia the bulk of the ovum bears so 

 small a proportion to its containing follicle, 

 that the ovum itself contributes in no degree 

 to the rupture by which it is enabled to 

 escape. In this process it remains a passive 

 bod)', at least in a mechanical point of view, 

 though doubtless it is the perfecting of 

 the ovum which gives the vital impetus to 

 that series of changes by which it is finally 

 released from its first abode. But the act of 



* I have anglicised the French term oviponte (ovi- 

 pont), to express tbe escape of the ovum from the 

 ovary; while "ovulatiou" is employed, in a more 

 general sense, to include also the process of its 

 maturation. 





