INSPIRATION. 387 



different amounts of oxygen and have different "specific oxygen 

 capacities," by which he means the ratio between the number of grams 

 of iron and the number of cubic centimeters of oxygen present in a 

 given volume of blood. The capacity of corpuscles for holding oxygen 

 is nicely demonstrated by the following simple experiment: Serum, 

 without corpuscles, is agitated in the presence of oxygen. The amount 

 of oxygen absorbed is found to be less than half what would be taken 

 up by the same amount of serum containing red corpuscles. 



The oxygen, being preferably united with the corpuscles, is 

 joined to them in a very unstable combination. The affinity is just 

 strong enough to facilitate the conveyance of the gas in the circula- 

 tory system, yet not so strong but that it may attack the combustible 

 materials of the tissues. 



However, it must be kept in mind that some of the oxygen is 

 contained in the blood-plasma., where it is in simple solution and 

 obeys the laws of Dalton. 



Ehrlich injected methylene blue into the vein during life. 

 After death the blood was found to be blue in color, and the other 

 tissues, especially the glandular, to be without color. Here the 

 avidity of the tissues for oxygen has removed this from the methy- 

 lene blue, which then becomes colorless. After a time the oxygen 

 in the air is absorbed and methylene blue is again formed. 



A curious phenomena of respiration in the tissues is that the 

 exhalation of carbon dioxide does not directly depend upon the pres- 

 ence of oxygen. For fragments of tissue, when placed in an atmos- 

 phere absolutely deprived of oxygen, as in hydrogen, continue to 

 produce carbonic acid. Engelmann and Pfluger hold that the proto- 

 plasm of the cells when exposed to oxygen has the power of storing it 

 up in an intramolecular form. Respiration is not so simple as it 

 appears to be: the oxygen absorbed is not immediately transformed 

 into carbonic acid. 



The cells of the tissues determine the amount of oxygen 

 required and not the amount of oxygen available. Inhalations of 

 pure oxygen do not augment the oxidation in the tissues. 



The intracellular ferments change and oxidize the dead food- 

 materials in the extracellular lymph which bathes them, just as has 

 been shown that the yeast-cells break up the sugar surrounding them 

 by their intracellular ferment, zymase, forming carbonic acid and 

 alcohol. The animal tissues are like the yeast-cell, which obtains 

 its oxygen, when deprived of it, by taking oxygen from that con- 

 tained in the sugar, for the animal tissues are anaerobic, as they 



