A text-book of human physiology : designed for the use of practitioners and students of medicine / by Austin Flint.

  • Flint, Austin, 1836-1915.
Date:
1876
Catalogue details

Licence: Public Domain Mark

Credit: A text-book of human physiology : designed for the use of practitioners and students of medicine / by Austin Flint. Source: Wellcome Collection.

Provider: This material has been provided by The University of Leeds Library. The original may be consulted at The University of Leeds Library.

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    wliat less in the female than in the male. Its density varies greatly under different con- ditions of digestion. ' . noo ^ ^ao Temperature.—ThQ temperature of the blood :s generally given as from 98 to 100 Fahr • but recent experiments have shown that it varies considerably in different parts of the circulatory systsm, independently of exposure to the refrigerating influence of the atmosphere By the use of very delicate registering thermometers, Bernard has suc- ceeded in establishing the following facts with regard to the temperature in various parts of the circulatory system in dogs and sheep: • 1. The blood is warmer in the right than in the left cavities of the heart. 2! It is warmer in the arteries than in the veins, with a few exceptions. 3. It is generally warmer in the portal vein than in the abdominal aorta, indepen- dently of the digestive act. 4. It is constantly warmer in the hepatic than in the portal veins. He found the highest temperature in the blood of the hepatic vein, where it ranged from 101° to 107°. In the aorta, it ranged from 99° to 105°. We may assume, then, in general terms, that the temperature of the blood in the deeper vessels is from 100° to 107° Fahrenheit. Color of the mood.—The color of the blood is due to the corpuscles. In the arterial system it is uniformly red. In the veins it is generally dark blue and sometimes almost black. This difference in color between the blood in the arterial and In the venous sys- tem was a matter of controversy at the time of Harvey. By the discoverer of the cir- culation, the difference, which is now universally known and admitted as regards most of the veins, was supposed to be merely accidental and dependent on external causes. Fifty years later, Lower demonstrated the change of color in the blood as it passes through the lungs, and associated it with the true cause; viz., the absorption of oxygen. The color in the veins, however, is not constant. Many years ago, John Hunter ob- served, in a case of syncope, that the blood drawn by venesection was bright red; and more recently, Bernard has demonstrated that, in some veins, the blood is nearly if not quite as red as in the arterial system. The color of the venous blood depends upon the condition of the organ or part from which it is returned. The red color was first no- ticed by Bernard in the renal veins, where it contrasts very strongly with the black blood in the vena cava. He afterward observed that the redness only existed during the functional activity of the kidneys; and when, from any cause, the secretion of urine was arrested, the blood became dark. He was led, from this observation, to examine the venous blood from other glands ; and, directing his attention to those which he was able to examine during their functional activity, particularly the salivary glands, he found the blood red in the veins during secretion, but becoming dark as soon as secretion was arrested. These observations may be easily verified by opening the abdomen of a living animal, exposing the renal veins, and introducing a canula into the ureter, so as to be able to note the fiow or arrest of the urine. So long as the urine continues to flow, the blood in these vessels is bright red; but when secretion becomes arrested, as it soon does after exposure of the organs, it presents no difference from the blood in the vena cava. In the submaxillary gland, by the galvanization of a certain nerve which he calls the motor nerve of the gland, Bernard has been able to produce secretion, and, by the galvanization of another nerve, to arrest it; in this way changing at will the color of the blood in the veiii. It has been found by the same observer that division of the sympathetic in the neck, which dilates the vessels and increases the supply of blood to one side of the head, produces a red color of the blood in the jugular. He has also found that paralysis of a member by division of the nerve has the same effect on the blood returning by the veins. The explanation of these facts is evident when we reflect upon the reasons'why the blood is red in the arteries and dark in the veins. Its color depends upon the corpus- cles ; and as the blood passes through the lungs it loses carbonic acid and gains oxygon.