File:Quain's elements of anatomy (1882) (14780424725).jpg

Identifier: quainselementsof82quai02 (find matches)
Title: Quain's elements of anatomy
Year: 1882 (1880s)
Authors: Quain, Jones, 1796-1865 Thomson, Allen, 1809-1884 Sharpey-Schäfer, E. A. (Edward Albert), Sir, 1850-1935, ed Thane, George Dancer, 1850-1930
Subjects: Human anatomy Anatomy
Publisher: London : Longmans, Green
Contributing Library: Francis A. Countway Library of Medicine
Digitizing Sponsor: Open Knowledge Commons and Harvard Medical School

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ts ofa set of segmental tubes developed in connection with this duct, pos-sessing the same glandular and glomerular structure as the mesonephros,and occupying a situation which is on the dorsal aspect of the Wolffianduct and near its hinder part. The characteristic feature in the develop-ment of the urino-genital system in the amniota is according to Balfourthe formation of a metanephros or permanent kidney, and the completeor partial disappearance of the other two parts of the segmental organs—viz., the pronephros and mesonephros. The Miillerian and Wolffian ducts stand in a different relation to theproductive organ in the two sexes. In the female the Miillerian ductbecomes developed into the whole length of the genital passages, and theWolffian duct almost entirely disappears. In the male, on the otherhand, the Wolffian duct becomes con^erted into the excretory duct (vasdeferens) of the testicle ; while the Miillerian duct undergoes atrophy andhas no permanent existence. Fig. 801.
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Fig. 801.—Diagram of the arrangement of the urino-genital organs in an ADULT FEMALE ELASMOBRANCH (frOm Balfour). m.d., Miillerian duct; iv.d, WolfEan duct; s.t, segmental tubes ; five of them arerepresented with openings into the body cavity, and five posteriorly correspond to themetanephros ; ov, the ovary ; d, ureter.- In connection with the conducting passages of both sexes there arefound in later life vestiges of those of the embryonic structures whichare not employed in the production of the permanent generative organs,and these vestiges are of considerable interest in their bearing upon thehistory of the changes by which the permanent organs are formed. Gejiital Ridge and Germ-Epithelium.—In all the Vertebrates theproductive gland of the generative system, ovary or testicle, takes itsorigin from formative blastema situated on the mesial side of eachWolffian body or mesonephros at an early period of embryonic life, andthere is in the commencement a close connection between th

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