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) (14802609723).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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ranous organ, providedinternally with longitudinal folds of the lining membrane, theanalogue of the leaflet, or manyplies, and, lastly, into a fourth, GASTEROPODOTJS MOLLUSCA.. 169 or true chylific membranous stomach ; the second chamber istraversed by a muscular gutter, leading from the first to thethird stomach. The digestive organs of Aplysia Camelus (sea hare, fig. 1/7)are not less singular,being not only equallycomplex, but in addi-tion, having the inter-nal membrane of thesecond stomach, or giz-zard, armed with carti-laginous bodies. Thepharynx (a) is large andmuscular ; the straightesophagus (b) havingtraversed the nervouscollar (m), soon dilatesinto an ample membra-nous crop (o, o\ turnedinto a semilunar form.This leads into a strongmuscular gizzard (p),internally armed withrhomboidal semi-cartila-ginous plates, their ac-tion being analogous tothe teeth found in thestomach of the lobster,and, like them, perform-ing a similar bruisingfunction. This muscu- lo-cartilaginous organ
Text Appearing After Image:
Fig. 177.—The anatomy of the AplysiaCamelus. opens into a third chylific stomach (</), the in-ternal surface of whichis furnished with sharp recurved horny spines, most numerousaround the pyloric orifice ; into this region of the canal theducts from the liver (u, «), and the termination of a glandularcsecal appendage, the pancreas, pour their secretions. It isextremely interesting, in a physiological point of view, to study 170 OEGANS OF DIGESTION. the development of the glandular organs connected with theassimilating functions. In Holothuria we have seen salivaryvessels developed in the form of a series of blind processessurrounding the mouth. In the mollusca these organs areglandular, and extend through nearly half the body in Aplysia(s, v) ; the liver in the mollusca is likewise glandular, whilstin the articulated animals it is composed of a series of con-voluted vessels. A rudimentary pancreas exists in somemollusca, which, like the salivary vessels in Holothuria,assumes the

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