File:Outlines of comparative physiology touching the structure and development of the races of animals, living and extinct - for the use of schools and colleges (1870) (14802661463).jpg

Identifier: outlinesofcompar00agas (find matches)
Title: Outlines of comparative physiology touching the structure and development of the races of animals, living and extinct : for the use of schools and colleges
Year: 1870 (1870s)
Authors: Agassiz, Louis, 1807-1873 Gould, Augustus A. (Augustus Addison), 1805-1866 Wright, Thomas, 1809-1884
Subjects: Physiology, Comparative Zoology
Publisher: London : Bell & Daldy
Contributing Library: MBLWHOI Library
Digitizing Sponsor: MBLWHOI Library

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f-like ends nowundergo transform-ation into blind vesi-cles, whilst the branch-es and twigs of thetree become hollow,and unite themselves to Fig. 276.—First appearance of the parotid the excretory duct (fig.gland in a human embryo of the seventh 277). The blood-week ; magnified twice. vessels are seen enter-ing the blastema in theshape of dark ramifica-tions (fig. 277), but ofmuch smaller diame-ters than those of theramified glandularcanal. The finest ele-ments of the secretingfollicles do not consistproperly of cells; inthe liver, for example(fig. 2/8), they are ex-tremely soft, roundish,granular corpuscles,which give to the largerlobules (A) a racemi-form appearance. Itis betwixt these majordivisions or lobulesthat the blood-vesselsmake their entrance Fig. 277.—Lobules of the parotid gland (fig- 278, B, «, «), wiih the excretory ducts from the embryo of a none ever penetrating sheep four inches long, magnified eight times, betwixt the finest ele- After Muller. ments of all>
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DISTRIBUTION OF VESSELS IN GLANDS. 269 DISTRIBUTION OF THE VESSELS IN GLANDS. (§ 428. Glands in general derive their blood from arteries,and all that is not used for purposes of secretion returns inthe usual way through veins and lymphatics into the generalcurrent of the circulation. The lymphatics of glands are oftenvery large and conspicuous ; those of the liver are particularlyso. Among vertebrate animals the liver receives but a smallportion of its blood from an arterial source, and this appearsto be exclusively expended upon the gall-bladder, the gall-ducts, and the coats of the larger vascular trunks, thoughbranches of the hepatic artery can also be followed, enteringalong with the cellular substance of the organ between itsseveral component lobules. The blood from which the bile isprepared is received from the portal vein, which ramifiesthrough the substance of the liver, and at length anastomoseswith the finest subdivisions of the hepatic vein, which springfrom the deeper par

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