CHANGES IN THE GASES OF THE BLOOD. 833 



The influence of oxygen, in increasing the amount of fibrin, has been 

 shown, by causing rabbits to breathe pure oxygen for a short time, 

 and also by inducing an unusual activity of the respiratory movements 

 by means of electricity applied to the spine and chest. In these 

 experiments, the quantity of fibrin in the arterial blood was increased 

 respectively to 2.4 and 2.9 parts in 1000 of blood; whereas in the 

 ordinary arterial blood, the proportion found was only 1.65. (Gardner.) 

 The fibrin is, of course, produced at the expense of some other albu- 

 minoid body, either globulin or albumen. Even out of the body, a 

 substance somewhat like fibrin, though not positively determined to be 

 fibrin, has been produced by transmitting oxygen gas (A. H. Smee), or 

 ozone (Gorup-Besanez), through a solution of albumen. 



Change in the Temperature of the Blood. 



Numerous attempts have been made, to determine whether there be 

 any difference, and if so, what difference, between the temperature of 

 the blood, before and after it has passed through the lungs. The older 

 physiologists, and also some recent observers (Harley and Savory), 

 have maintained that the blood in the left ventricle is warmer, by from 

 1 to 2, than that in the right ventricle; and, in accordance with this, 

 it has often been supposed that the oxygen combined directly with 

 certain constituents of the blood in the lungs, to produce the whole of 

 the carbonic acid given off in respiration. But it is now known that 

 this latter supposition is incorrect. Many observers, moreover, have 

 found that the blood in the left side of the heart, is not so warm as 

 that in the right cavities, owing, as they maintain, to a cooling pro- 

 cess, caused by the entrance into the lungs of air of a lower tempera- 

 ture than the blood, and by the evaporation of moisture from the 

 internal pulmonary surfaces. This does not affect the general conclu- 

 sion, that the venous blood returning from the limbs, is cooler than 

 the arterial blood of the same parts. We shall revert to this subject 

 in the Section on Animal Heat. 



Changes in the Gf-ases of the Blood. 



It has been elsewhere noticed (pp. 614, 616) that the vapor of water 

 and also many volatile substances and gases are readily absorbed into 

 the blood by the lungs ; and, indeed, one of the two chief phenomena 

 of respiration, viz., the entrance of oxygen into the blood, illustrates 

 the absorptive power of the pulmonary mucous membrane. 



This absorption of oxygen from the inspired air by the venous blood 

 brought to the pulmonary capillaries, is associated with the evolution 

 of carbonic acid which escapes from that venous blood, and is added to 

 the air about to be expired. These two joint interchanges of the gas- 

 eous elements of the air and of the blood are essential steps in the con- 

 version of venous into arterial blood. That the blood participates in 

 these changes is shown by the fact that venous blood contains less 

 oxygen and more carbonic acid than arterial blood, which, on the other 



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