The elements of embryology. / By M. Foster ... and Francis M. Balfour.

  • Michael Foster
Date:
1874
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Licence: Public Domain Mark

Credit: The elements of embryology. / By M. Foster ... and Francis M. Balfour. Source: Wellcome Collection.

Provider: This material has been provided by The University of Leeds Library. The original may be consulted at The University of Leeds Library.

    193/336 (page 167)
    'VI.] THE TESTES. 1G7 Pfliiger {iHe Eierstocke der SdugetMere u. des Menschen, Leipzig, 1853) de- ! scribed the ova as arising, in mammals, out of the epithelium of tubular glands, . a chain of several ova being frequently found in one tube and the tube be- i coming subsequently divided by constrictions into as many follicles. According to Waldeyer however, whose account we have followed above, the primordial ■ ova make their appearance as individual specialized epithelium-ceUs, without the preformation of any tubular glands, the capsule or Graffian follicle being a later product. Waldeyer's views have been on the whole generally accepted (Leo- pold, Untersuch. uber das Epithel. des Ovariums. Inaug. Diss. Leipzig, 1870, Eomiti, Max Schultze's Archiv, 1873, Bd. x.), though opposed by Kapff {Rei- chert and Du Bois Reymond's Archiv, 18^2), and more recently by Sernoff {loc. cit.). The first traces of the testes are found in the dorsal and inner side of the intermediate cell-mass, and appear about the sixth day. From the first they differ from the rudimentary ovaries, by coming into somewhat close connection with the WoMan bodies ; but occupy about the same limits from before backwards. The mesoblast in the position we have mentioned begins to become somewhat modified, and by the eighth day is divided by septa of connective tissue into a number of groups of cells ; which are the commencing tubuli seminiferi. By the sixteenth day the cells of the tubuli have become larger and acquu-ed a distinctly epithelial character. Waldeyer is of opinion that the tubules of the WolfiBan body penetrate into the tissue from which the testes are formed, and becoming much finer than the remainder of the tubules constitute the 'tubuli seminiferi.' Apart from its inherent difficulties, this view has not been corroborated by any subsequent observer. It is distinctly denied by Sernoff {loc. dt), who further states that the testes are entirely formed out of the mesoblast of the intermediate cell-mass, and that their rudiments have no connection either with the germinal epithelium or with the tubules of the Wolffian body. We have now described the origin of all the parts which form the urinary and sexual systems, both of the embryo and adult. It merely remains to speak briefly of the changes, which on the attainment of the adult condition take place in the parts described. The Wolffian body, according to Waldeyer, may be said to consist of a sexual and urinary part, which can, he states, be easily distinguished in the just-hatched chick. The sexual part becomes in the cock the after-testes or coni vasculosi, and consists of tubules which lose themselves on the one hand in the seminiferous tubules, and on the other hand, in birds, probably form the whole of what can be called the epididymis. In the hen it forms part of the parovarium of