94 PHYSIOLOGICAL CHEMISTRY. 



the cause of coagulation has been just as little proved as the asser- 

 tion that the coagulation of milk in the preparation of cheese is 

 produced by the calcium phosphate becoming insoluble without 

 the action of the rennet ferment on the casein. The untenability 

 of FREUND'S theory has been shown by LATSCHENBERGER. 



According to DOGIEL and HOLZMANN, the coagulation of the 

 fibrin is an oxidation of the fibrinogen. The relation of oxygen to the 

 coagulation is not quite clear; a certain influence, however, on the 

 coagulation cannot be denied. But as the coagulation may take 

 place also in the absence of free oxygen, the above statement seems 

 not to be well grounded. 



The very dark and complicated process of the intravascular 

 coagulation and the relationship of the so-called tissue fibrinogen 

 (WOOLDRIDGE) to the same have been so insufficiently studied that 

 we cannot enter here into a discussion of this interesting question. 



IV. The Gases of the Blood. 



Since the pioneer investigations of MAGNUS and LOTHAR 

 MEYER the gases of the blood have been subjects for repeated, care- 

 ful investigations by prominent experimenters, among whom we 

 must mention first C. LUDWIG and his pupils and E. PFLUGER 

 and his school. By these investigations not only has science been 

 enriched by a mass of facts, but also the methods themselves have 

 been made more perfect and accurate. In regard to these methods, 

 as also in regard to the laws of the absorption of gases by liquids, 

 dissociation, and other questions belonging here, the reader is 

 referred to complete text-books on physiology, on physics, and on 

 gasometric analysis. 



The gases occurring in blood under physiological conditions are 

 oxygen, carbon dioxide, and nitrogen. The last-mentioned gas is 

 only found in very small amounts, on an average of 1.8 vol. per cent. 

 The amount is here, as in all following experiments, calculated for 

 C. and 760 mm. pressure. The nitrogen seems to be simply ab- 

 sorbed into the blood, at least in great part. It appears to play no 

 part in the processes of life, and its amount varies but slightly in 

 the blood of different blood-vessels. 



The oxygen and carbon dioxide behave otherwise, as their 



