Magazine of Natural History (Volume 5) (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1832. Excerpt: ... Art. VI. An Introduction to the Natural History of Molluscous Animals. In a Series of Letters. By G. J. Letter 9. On their Circulating System. Sir, Aristotle divides animals into those which have blood, and those which have none; and these primary classes were appropriately named the sanguineous and exsanguineous. Among the latter he places the Mollusca, as all naturalists did for a long time afterwards, and as all, except naturalists, continue to do. Blood is scarcely known to the vulgar unless by its red colour; and so essential is this character deemed, that it appears to them little less than an abuse of language to apply the term to any white or colourless fluid. Even Linnaeus seems to have participated of this prejudice, and to have yielded to its influence, when he called the circulating fluid of the Mollusca a sanies: but to call it any thing else than blood is apt to lead into error; for it possesses all the essential properties of blood, flows in an analogous circle of vessels, and answers the same purposes in the system. The circulating system of the Mollusca consists of a heart, either single, or with its parts disjoined; and of two kinds of vessels, viz. arteries and veins: and the latter are supposed to perform the additional function of absorbents; for nothing analogous to these has been yet detected. The heart is very various in point of figure, but is always evidently muscular, and has its interior strengthened with fleshy cords (columns? carneos), interlaced in every direction. (Jig. 24. ) It is placed in general in the back, above the alimentary canal, near to or between the branchiae, and in a cavity usually called the pericardium, and considered, according to Blainville erroneously (Manuel de Malacologie, &c, p. 131.), as the represen...