OVARY (NORMAL ANATOMY). 



551 



nancy, and which result in the formation of 

 the body termed the corpus lulcuin. 



Without entering upon the question of the 

 number of laminae into which the walls of a 

 Graafian follicle may be split by skilful mani- 

 pulation, it will suffice to consider those only 

 as distinct membranes or coats, which exhi- 

 bit obvious differences of structure and rela- 

 tionship, during the various phases of develop- 

 ment and decay which the follicle undergoes 

 from its first formation to its final disappear- 

 ance. In this view the walls of the Graafian 

 follicle must be regarded as being composed 

 of three membranes ; and indeed but for the 

 importance attached to the use of the third or 

 innermost of these, which in any case is hardly 

 more than a thin layer of granules, it would 

 have sufficed if the coats of the vesicles had 

 been enumerated as two only. 



The external fibrous or vascular coat (fig. 

 374. u,fig- 371. E) constitutes the tunic of the 

 ovisac of Barry, the tunica fibrosa, S. thecafol- 

 liculi of Baer. It forms no portion of the ori- 

 ginal ovisac, but is a superadded part, derived 

 from the parenchyma of the ovary. This 

 coat closely embraces the ovisac, and partakes 



Fig. 374. 



Graafian vesicle of the rabbit x 100 (?) diameters. 

 (After Barry.) 



a, outer coat or tunic of the ovisac ; b, ovisac ; 

 c, epithelial lining or membrana granulosa, a por- 

 tion of which has been removed in order to display 

 del, retinacula (here too distinctly marked) ; e, tunica 

 granulosa of Barry immediately surrounding the 

 ovum, consisting of, /, zona pellucida, within which 

 is the yelk and germinal vesicle and macula. 



in its spherical figure ; it carries numerous 

 blood-vessels, which pass from the ovarian 

 stroma to become expanded in a vascular net- 

 work over its walls (fig. 371. D). 



Examined by the microscope, this membrane 

 is seen to be highly vascular. It is composed 

 of a fine membrane, containing few fibres, but 

 everywhere abundantly studded with oval 

 nuclei, visible without the aid of acetic acid, 

 and probably, in part at least, due to the pre- 

 sence of so many blood-vessels in its tissue. 

 This coat contains no oil globules. Its chief 

 use appears to be to give increased support 

 and protection to the true ovisac which it sur- 

 rounds, and to convey blood-vessels from the 

 ovary for its nutrition, and for the supply of 

 the fluids which the ovisac contains. 



The second or internal coat, as it is com- 

 monly termed, of the Graafian follicle is the 

 ovisac itself. It constitutes at first an inde- 



pendent structure; but receiving afterwards 

 the before mentioned investment from the 

 ovarian parenchyma, the two coats unite to 

 form the Graafian follicle. The ovisac is. 



Fig. 375. 



Structure of ovisac. (Ad J\'at. x 3.30.) 



composed of embryonic fibres of connective 

 tissue (fig. 375. a), of rounded cells or 

 granules, b; and of a large proportion of minute 

 oil globules, c. The embryonic fibre-cells lie 

 parallel with each other, and together with the 

 granules form the bulk of the tissue in nearly 

 equal proportions. The oil drops are very 

 numerous ; and after the preparation has been 

 under examination for some time they are seen 

 to float up to the surface of the drop of water 

 in which it is placed, and to collect upon the 

 under side of the glass disc used for covering it. 

 In addition to these there is found a small quan- 

 tity of developed fibres of connective tissue, 

 which appear to give firmness to the whole. 

 The Graafian follicle thus composed, contains, 

 in close contact with its inner wall, a stratum 

 of nucleated cells, forming an epithelial lining, 

 termed the membrana granulosa (fig. 374. c, 

 fig. 371. G). The cells or granules which give a 

 name to this membrane are so lightly held to- 

 gether that it has beendoubted whether the stra- 

 tum which they form is really entitled to the 

 denomination of a membrane. Nevertheless this 

 structure appears to play an important part in 

 regard to the ovum, which is always found 

 lodged within a portion of it. At the com- 

 mencement of the formation of the ovisac, ac- 

 cording to Dr. Martin Barry, these peculiar 

 elliptical nucleated cells or granules are nearly 

 equally diffused through the fluid which it con- 

 tains, the ovum lying in their centre. But 

 about the time at which the ovisac unites with 

 its covering or tunic to form the Graafian fol- 

 licle, these granules are found to have become 

 separated into little groups, leaving interspaces 

 filled by fluid. Further, as this separation ad- 

 vances, the granules arrange themselves in such 

 a manner as to constitute three distinct struc- 

 tures. The principal portion collects upon the 

 inner surface of the ovisac forming the mem- 

 brana granulosa just described (fig. 374. c]. 

 A second portion becomes aggregated upon 

 and around the ovum, taking its form and 

 constituting a special investment for it. This 

 is the tunica granulosa of Barry (fig. 374. e). 

 A third portion collects to form a structure 

 composed of a central mass in which the 

 ovum with its tunica granulosa is imbedded, 

 corresponding with the cumulus (Jig. 371. 

 H,II) of Baer, and of certain cords or flattened 

 bands, from two to four in number, which pass 

 off from the central mass outwards, to become 

 united with the layer of granules lining the 

 follicle. These radiating bands or cords arc 

 termed by Barry the retinacula, (fig. 37k </</) 



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