. A text-book of comparative physiology for students and practitioners of comparative (veterinary) medicine. Physiology, Comparative. 226 COMPARATIVE Fig. 196.—Circnlatioa in the wob of a frog's foot (Wagner). V, venons trunk com- posed of the three principal branches (?j, v, v") covered with a plexus of smaller ves- sels. The whole is dotted over with pigment masses. THE CHARACTERS OF THE BLOOD-FLOW. If an artery be opened, tlie blood is seen to flow from it in a constant stream, with periodic exaggerations, which, it is found, answer to the heart-beats ; in the case of vein
. A text-book of comparative physiology for students and practitioners of comparative (veterinary) medicine. Physiology, Comparative. 226 COMPARATIVE Fig. 196.—Circnlatioa in the wob of a frog's foot (Wagner). V, venons trunk com- posed of the three principal branches (?j, v, v") covered with a plexus of smaller ves- sels. The whole is dotted over with pigment masses. THE CHARACTERS OF THE BLOOD-FLOW. If an artery be opened, tlie blood is seen to flow from it in a constant stream, with periodic exaggerations, which, it is found, answer to the heart-beats ; in the case of veins and xjapillaries the flow is also constant, but shows none of the spurting of the arterial^stream, nor has the cardiac beat appar- ently an equal modifying effect upon it. We have already explained why the flow should be constant, though it would be well to be clearer as to the peripheral re- sistance. The amount of friction from linings so smooth as those of the blood-vessels can not be considerable. Whence, then, arises that friction which, keeps the arterial vessels always distended by its backward influence ? The microscopic study of the circulation helps to answer this question. The plas- ticity of the corpuscles and of the vessel walls themselves must be taken into account, in consequence of which a dragging influence is exerted whenever the corpuscles touch the wall, which must constantly happen with, vast numbers of them in the smallest vessels and especially in the capillaries. The arrangement of capillaries into a mesh-work, must also, in. 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 original Mills, Wesley, 1847-1915. New York, Appleton
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