The laws and mechanics of circulation, with the principle involved in animal movement . ral canals the blood is madeperpetually to pass and repass the respiratory sacculi ; and,opposite to each of these, branches are given off which formso many independent vascular circles, representing very closelythe minor or pulmonary circulation of higher animals. Finally, the rich supply of arterialized blood sent to thelateral caeca of the stomachal cavity for promoting the secre-tory processes in these organs in connection with digestion, has * Ann. des Sci. Nat., vol. xv. NO HEAET I INT THE LEECH. 385
The laws and mechanics of circulation, with the principle involved in animal movement . ral canals the blood is madeperpetually to pass and repass the respiratory sacculi ; and,opposite to each of these, branches are given off which formso many independent vascular circles, representing very closelythe minor or pulmonary circulation of higher animals. Finally, the rich supply of arterialized blood sent to thelateral caeca of the stomachal cavity for promoting the secre-tory processes in these organs in connection with digestion, has * Ann. des Sci. Nat., vol. xv. NO HEAET I INT THE LEECH. 385 forcible illustration in the beautiful arborescent arrangementof the vessels in the walls, with their footstalks connectingimmediately with the dorsal artery (Fig. 155, g, a). The fol-lowing illustration (Pig. 156) will give some idea of the rela-tions the csecal pouches (7c) sustain to the stomachal cavityand respiratory vesicles ; the stomach itself occupying abouttwo-thirds of the visceral cavity, is divided by septa or dia-phragms into nine or ten compartments, but communicating. Fig. 155.—Diagram Illustrative of the Circulation in the Leech.—Dr. Williams, a,Great dorsal vessel; c, ventral vessel ; d, d, intercommunicating vessels betweendorsal and ventral trunks; e, e, lateral abdominal trunks ; g, vessels distributedover the caecal appendages to the stomach ; /, /, /, loop-shaped organs to the respira-tory vesicles ; h, h, lateral branches to respiratory vesicles. freely with each other, and in each of which are two openingscommunicating with the lateral caeca. Up to this stage in development, then, in which a very com-plex circulation is seen to exist, no heart presents, but the ves-sels themselves producing it, inclusive, of course, of the actionof the polar forces. Unless, forsooth, the whole dorsal vessel,running the length of the body, inclusive of the lateralbranches, be considered as such, which is perfectly absurd—the outcome, in fact, of the misleading and
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Keywords: ., bookcentury1800, bookde, booksubjectblood, booksubjectrespiration
