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A Text-Book of Pathological Anatomy and Pathogenesis
A TextBook of Pathological Anatomy and Pathogenesis Author:Unknown Author Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: CHAPTER III. CHANGES IN THE QUANTITY AND COMPOSITION OF THE BLOOD. 258. We have already said (Art. 251) that the blood is a liquid tissue .whose quantity a... more »nd composition are normally constant, within narrow limits. This constancy of the blood is maintained by the physiological adjustment of the matter asssimilated and the matters eliminated, and by the speedy rejection of any abnormal matters which may gain entrance. In disease, the equilibrium may be disturbed, so that the quantity and the chemical constitution of the blood may deviate from the normal for a longer or shorter time. Increase in the quantity of blood in the body, i. e., a true hyperplasia or plethora, does not occur as an abiding condition. When, for example, after amputation by the bloodless method (in which the blood contained in the limb is pressed back into the body before operation), the quantity in the body is rendered relatively excessive, the surplus is rapidly used up, and is not replaced. True plethora or polyaemia is in fact an essentially transient condition. The opposite condition, namely, decrease in the quantity of blood, is called oligaemia or anaemia. Every abnormal loss of blood produces a temporary anaemia. If this does not exceed a certain limit, and if there is nothing to interfere with the production of blood, the loss is soon made up, and the anaemia is transient. But if the loss is greater, or often repeated, or long-continued, the anaemia may become chronic. During life, this condition is indicated by the pallor of the skin and mucous membranes; post-mortem it appears in the small proportion of blood contained in the several organs. After a loss of blood, the replacement of the liquor aanguinis proceeds more rapidly than the replacement of the red corpuscles. For a time, there...« less