THE PAEOYAEIUM. 479 



Valentin (Miiller's Ai-chiv.. 1838, p. 526), and since maintained as the result of 

 careful observation by Pfliiger (1863). that the ova are at first formed in groups 

 \\'ithin tubes, which thus constitute an original and characteristic feature in the 

 stmctm-e of the ovary. 



By the elaborate researches of Waldeyer (Eier.stock und Ei, Leipzig, 1870. and 

 in Strieker's Handbuch, p. .568.) it was ascertained that the ovigerms or primordial 

 ova derive their origui from the superficial layer of cells or germ epithelium, 

 covering the mass of blastema which lies to the mside of the "Wolifian body, and 

 which constitutes the common germinal matrix of the ovary and testicle. 

 According to AValdeyer's observations, while the o\agerms themselves come from 

 the superficial epithelium, and thus exist from an early period of foetal life, 

 the Graafian follicles owe their origin to an outgro'^'th of the subjacent vascular 

 connective tissue which constitutes the ovarian stroma. Brush-like lU'ocesses of 

 this tissue growing out from the surface, involve in their meshes the enlarged 

 epithelial cells which form the commencing ova. and at the same time enclose 

 groups of other less developed epithelial cells, which come to be an-anged round 

 the larger ovigerms, and thus constitute the commencement of the cells of the 

 membrana granulosa. According to Waldeyer's view, therefore, both the pri- 

 mordial ova and the cells of the membrana granulosa sirring from the germ- 

 epithelium of the reproductive blastema, while the wall of the Graafian follicle 

 is a production of the vascular connective tissue of the stroma. 



A somewhat different view has been presented by KoUiker. as the result of 

 observations made on the foetus of several animals (Sitz. der Phys. Med. Gesellsch. 

 in Wurtzburg, May. 1874) : for while he agrees with Waldeyer in referring the 

 first origin of the ova to the germ epithelium, he is inclined to consider the 

 membrana gi-anulosa as proceeding from other cellular elements, existing in con- 

 nection with the ovarian stroma. These cellular elements, he conceives, are 

 contained in a set of medullaiy cords or canals extending upwards into the ovary 

 from its attached border, and they fmiiish the cellular coverings to the primor- 

 dial ova by spreading outwards upon them, and enclosing them, first in groups, 

 and later each one singly. He regards these cords as the same which have l^een 

 described as the epoophoron or remains of the "Wolflaan body in the ovarj'. 



These diff'erent views appear to be in some measure reconciled, and new light 

 thrown upon the subject, by the independent observations of James Foulis. made 

 in the human foetus, and in calves and kittens, and which, from observation of 

 the specimens, the writer can in most points confinn (•' Development of Ova and 

 Structure of the Ovary,"' &c.. by Dr. James Foulis. in Proceed, of Boy. Soc. of Edin., 

 April, 1875). By these researches the origin of the ovigerms or i^rimordial ova 

 from the superficial germ epithelium is fully confiiined, and the stroma of the 

 ovary is shown to be prodr.ced by a direct growth from the sulijacent tissue 

 situated on the median side of the Wolffian body. The nucleus of each epithelial 

 corpuscle becomes the gemiinal vesicle of the primordial ovum : a nucleolus soon 

 appears within (the macula), and a clear homogeneous protoplasm collecting- 

 round the vesicle, fomis the commencement of the yolk. Tlie enclosure of the 

 primordial ova in a Graafian follicle takes place hj the outgrowth of processes 

 of the connective tissue of the stroma, so that the former, being surrounded 

 by these processes, become more and more embedded in the substance of the 

 ovary. At the same time, however, the germ-epithelium corpuscles increase in 

 number by prohf oration, and extending themselves inwards are in their turn 

 enclosed singly or in clusters by the processes of the stroma. But what is most 

 important and novel in these observations is this, that Dr. Foulis has traced the 

 fonnation of the cells of the membrana granulosa to the nuclei of the fibro- 

 nuclear tissue constituting the stroma, Which gradually insinuate themselves 

 round each primordial ovum, along with the processes of the vascular tissue of 

 the stroma which afterwards forms the wall of the follicle. The connective- 

 tissue nuclei which first surround each ovigerm are comparatively few in number ; 

 but they soon increase by cell multiplication, and form the complete membrana 

 gi-anulosa by which the follicle is lined. 



On the subject of the ovum, in addition to the works previously quoted, the 

 following may be mentioned : — Martin Ban-y"s Kesearches on Embiyology. in 



