The Anatomy And Physiology Of Capillaries

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1922 edition. Excerpt: ... LECTURE VI THE REACTIONS OF CAPILLARIES TO STIMULI (CONTINUED) Capillary poisons. AS a type of substances which show a selective / action on the contractile elements of the capiljLlary wall Heubner has studied the gold salt, AuCl4Na + 2H2O, and describes the effects of an intravenous injection of a lethal dose of this substance in mammals (rabbit, cat and dog). The lethal dose for a rabbit is about 15 mg. per kg. body weight. For the carnivora it is about three times as high. The arterial pressure begins to fall during the injection and continues to fall, reaching zero in a few minutes (not above ten), when the animal dies, though the heartbeat may continue for a short time afterwards. At autopsy the parenchymatous organs, as also the lungs and muscles, appeared to contain an abnormal quantity of blood, and bleedings from minute vessels were frequent. The intestines, especially the empty stomach, duodenum and jejunum, of the carnivora were abnormally injected with numerous patches of a deep red in the mucosa, in spite of the fact that the animals had been without food for a day before being used for the experiments. In several cases considerable quantities of blood were found in the abdominal cavity, though no macroscopic wounds could be detected. The microscopic examination of the organs showed dilated and very numerous capillaries and dilated venules and very numerous microscopic bleedings from capillaries and venules, especially in the liver, lungs and kidneys. The small arteries were everywhere contracted, in most cases even to obliteration of the lumen. These post-mortem observations, together with the sudden fall of arterial pressure preceding death, show clearly that we have to do with a relaxation of the capillaries and venules...

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This e-book will review special features of the cerebral circulation and how they contribute to the physiology of the brain. It describes structural and functional properties of the cerebral circulation that are unique to the brain, an organ with high metabolic demands and the need for tight water and ion homeostasis. Autoregulation is pronounced in the brain, with myogenic, metabolic and neurogenic mechanisms contributing to maintain relatively constant blood flow during both increases and decreases in pressure. In addition, unlike peripheral organs where the majority of vascular resistance resides in small arteries and arterioles, large extracranial and intracranial arteries contribute significantly to vascular resistance in the brain. The prominent role of large arteries in cerebrovascular resistance helps maintain blood flow and protect downstream vessels during changes in perfusion pressure. The cerebral endothelium is also unique in that its barrier properties are in some way more like epithelium than endothelium in the periphery. The cerebral endothelium, known as the blood-brain barrier, has specialized tight junctions that do not allow ions to pass freely and has very low hydraulic conductivity and transcellular transport. This special configuration modifies Starling's forces in the brain microcirculation such that ions retained in the vascular lumen oppose water movement due to hydrostatic pressure. Tight water regulation is necessary in the brain because it has limited capacity for expansion within the skull. Increased intracranial pressure due to vasogenic edema can cause severe neurologic complications and death.

Excerpt from The Anatomy and Physiology of Capillaries In the year 1883 a legacy of eighty thousand dollars was left to the President and Fellows of Yale College in the city of New Haven, to be held in trust, as a gift from her children, in memory of their beloved and honored mother, Mrs. Hepsa Ely Silliman. On this foundation Yale College was requested and directed to establish an annual course of lectures designed to illustrate the presence and providence, the wisdom and goodness of God, as manifested in the natural and moral world. These were to be designated as the Mrs. Hepsa Ely Silliman Memorial Lectures. It was the belief of the testator that any orderly presentation of the facts of nature or history contributed to the end of this foundation more effectively than any attempt to emphasize the elements of doctrine or of creed; and he therefore provided that lectures on dogmatic or polemical theology should be excluded from the scope of this foundation, and that the subjects should be selected, rather, from the domains of natural science and history, giving special prominence to astronomy, chemistry, geology and anatomy. It was further directed that each annual course should be made the basis of a volume to form part of a series constituting a memorial to Mrs. Silliman. The memorial fund came into the possession of the Corporation of Yale University in the year 1901; and the present volume constitutes the eighteenth of the series of memorial lectures. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.

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