Carpenter's principles of human physiology . rapid action. The increased rapidityof the pulse observed by Asp to follow excitation of the central extremity ofthe divided spinal cord has not been found to be constant by Dittmar,* thevariation being probably dependent upon the complicated effects of the increasedblood-pressure, which the latter experimenter has shown results from thisoperation. 3. Movement of the Blood in the Arteries. 233. The Blood propelled from the Heart is distributed to the body ingeneral by a system of Arteries, which may be likened in its arrangement tothe trunk and bran
Carpenter's principles of human physiology . rapid action. The increased rapidityof the pulse observed by Asp to follow excitation of the central extremity ofthe divided spinal cord has not been found to be constant by Dittmar,* thevariation being probably dependent upon the complicated effects of the increasedblood-pressure, which the latter experimenter has shown results from thisoperation. 3. Movement of the Blood in the Arteries. 233. The Blood propelled from the Heart is distributed to the body ingeneral by a system of Arteries, which may be likened in its arrangement tothe trunk and branches of a tree, except that very frequent communicationsor anastomoses exist among these branches, so that, by continual subdivisionand inosculation, their distribution comes more and more to resemble thecapillary network in which they terminate (Fig. 130). Although the diametersof the branches, at each subdivision, together exceed that of the trunk, yetthere is but little difference in their respective areas. What difference does Fig. Web of Frogs foot, stretching between two toes, magnified 3 diameters: showing the blood-vessels, and their anastomoses:—a, a, veins; b, b, b, arteries. exist, however, is, with few exceptions, in favour of the branches; and thusit happens that there is a gradual increase in the capacity of the arterialsystem from its centre towards the capillaries, whose capacity is many timesgreater. In passing from the Capillaries to the smaller arteries, the thin wallof the former, composed of a single layer of cells, becomes strengthened by asecond layer of flattened nucleated cells placed externally, and forming a tunica * Ludwigs Arbeiten, 1871, p. 18. MOVEMENT OP THE BLOOD IN THE ARTERIES. 305 adventitia; short unstriped muscle-cells also appear, which are at first irre-gularly distributed, but subsequently form a continuous circular layer—theTunica media. Between the muscle layer and the original endothelial wall ofthe capillary a delicate hyal
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectphysiology, bookyear1
