. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. 288 RESPIRATION. of the body receives blood directly from the cardiac ventricle. The carotids, the homo- logues of the subclavian, the hyo-opercular and orbito-nasal arteries proceed from the abdominal aorta at the point of confluence of the branchial veins. In these vessels, there- fore, the blood is arterialised, while its move- ment is impulsatile or venous. The pro- pulsive agents, under the form of diminutive lymphatic hearts, which Dr. M. Hall*, M. Fohmanf, and J. Miillerf have shown to guard the several points of
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. 288 RESPIRATION. of the body receives blood directly from the cardiac ventricle. The carotids, the homo- logues of the subclavian, the hyo-opercular and orbito-nasal arteries proceed from the abdominal aorta at the point of confluence of the branchial veins. In these vessels, there- fore, the blood is arterialised, while its move- ment is impulsatile or venous. The pro- pulsive agents, under the form of diminutive lymphatic hearts, which Dr. M. Hall*, M. Fohmanf, and J. Miillerf have shown to guard the several points of communication between the absorbent and venous systems, probably renders as great assistance in cir- culating the contents of the latter as those of the former orders of vessels. In the white- bait (Clupea alba of Yarrell) these micro- scopic hearts can be most perfectly observed. From a consideration of the preceding traits distinctive of the circulation of fishes, it will be afterwards shown that the laws of aquatic respiration are destined to receive new eluci- dation. Minnie Circulation of the Branchiae. — The branchial arteries proceed on either side, symmetrically, from the aorta, and travel through a groove along the convex border of the branchial arches, the veins lying to the outside of the artery, that is, next to the pec- tinated fringes of the gills. The cartilage system of the arches and that of the penknife- shaped processes (bearing the ultimate bron- chial leaflets) are quite distinct and uncon- nected save by fibrous structure. It is in the in- tervals between these solid parts that the trunks of the vessels are disposed. As the pectinated processes (a, fig. 235.) arise, when biserial, alternately from the arch, the arterial branches leading to them observe a similar arrange- ment. The arteries carrying venous blood invariably run along the thick border or outer margin of each process, the vein occupying the innermost edge. A branchial process, attached at r
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