456 RESPIRATION. 



undoubtedly true that the corpuscles, deprived of their natu- 

 ral plasma, are not changed in color by being exposed to the 

 air, or even to pure oxygen. Dr. Stevens, after removing 

 the serum from a clot by repeated washings with pure water, 

 found that the color remained black when exposed to the air, 1 

 but was reddened by the addition of its serum, or certain 

 saline solutions. From this he reasoned that the red color of 

 arterial blood is due to the saline constituents of the plasma. 

 This is true ; but the saline constituents of the plasma affect 

 the color indirectly, by maintaining the anatomical integrity 

 of the corpuscles. If blood be received from a vein into pure 

 water, it remains almost black, however long it may be ex- 

 posed to the air, 2 from the fact that the corpuscles are de- 

 stroyed. These facts are only additional evidence of the 

 function of the red corpuscles in absorbing oxygen and car- 

 rying it to the tissues. According to the late researches 

 of Fernet, which have been confirmed by L. Meyer, the vol- 

 ume of oxygen fixed by the corpuscles is about twenty-five 

 times that which is dissolved in the plasma. 3 



Comparison of ike Gases in Venous and Arterial Blood. 

 The demonstration of the fact that free oxygen and carbonic 

 acid exist in the blood, with a knowledge of the relative pro- 

 portion of these gases in the blood before and after its pas- 

 sage through the lungs, is a point hardly second in importance 

 to the relative composition of the air before- and after respi- 

 ration. The idea enunciated by Mayow about two hundred 

 years ago, that "there is something in the air, absolutely 



1 WILLIAM STEVENS, Observations on the Healthy and Diseased Properties of the 

 Blood, London, 1832, p. 862; and Philosophical Transactions, 1835. 



2 MILNE-EDWARDS, Physiologic, tome i., p. 475. 



3 LONGET, Traite de Physiologic, Paris, 1861, tome i., p. 595. Fernet made a 

 great number of experiments on the influence of the various salts contained in the 

 serum on the absorbing power of the blood for gases. His observations had par- 

 ticular reference to carbonic acid, the solubility of which was influenced most by 

 saline principles. These experiments were confirmed and extended by Lothar 

 Meyer (Die Gase dcs JBlutes). 



