. Animal physiology. Physiology, Comparative; Physiology, Comparative. 228 CIRCULATION IN MOLLUSC A. first of these arches supplies the vessels of the head, t t; which also, however, receives a branch o from the second arch. The second arch, after giving off that branch, unites with its fellow to form the aortic trunk a v. The third arch has completely shrivelled up. And the fourth arch or pulmonary artery has now attained its full size, and is become the sole channel through which the aeration of the blood is effected. 290. In the greater part of the Mollusca, the circulation takes place near
. Animal physiology. Physiology, Comparative; Physiology, Comparative. 228 CIRCULATION IN MOLLUSC A. first of these arches supplies the vessels of the head, t t; which also, however, receives a branch o from the second arch. The second arch, after giving off that branch, unites with its fellow to form the aortic trunk a v. The third arch has completely shrivelled up. And the fourth arch or pulmonary artery has now attained its full size, and is become the sole channel through which the aeration of the blood is effected. 290. In the greater part of the Mollusca, the circulation takes place nearly on the same general plan as in Fishes; the heart having two cavities, and the whole of the blood traversing both the respiratory and the systemic capillaries, between each time of its leaving the heart and returning to it again. But this heart is systemic, and not pulmonary; for it receives the arterial blood from the gills, and transmits it to the great sys- temic artery ; and after the blood has been rendered venous by its passage through the capillaries of the body, it enters the vessels which distribute it to the gills, before being again subjected to the action of the heart. The accompanying figure of the circulation in the Doris (a kind of sea slug) will serve to show the general distribution of the vessels in this group. The heart consists of a ventricle «, whence issues the main artery b; and of a single or double auricle c, in which terminate the veins, d, of the branchial apparatus e. The aerated blood which these convey to the heart, is transmitted by it, through the artery £>, to the system at large; and from this it is collected, in the state of ve- nous blood, by the veins Fig. 133.—Circulating Apparatus of Doris. , . which terminate in the large. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the origi
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Keywords: ., bookauthorcarpenterwilliambenja, bookcentury1800, bookdecade1840
