THE METABOLISM IN COMPRESSED AIR 237 



exchange, depresses the body temperature, and provokes con- 

 vulsions. These effects we will now consider in further detail. 



THE METABOLISM IN COMPRESSED AIR 



The rate at which fuel burns is increased by a greater supply 

 of oxygen, and it has commonly been held that the same holds 

 good for protoplasm. This, however, is not the case. It has 

 been proved that oxygen tensions between 11 per cent, and 94 per 

 cent, of an atm. have no influence on the rate of metabolism. 

 Within these limits the cell rules its own rate of metabolism 

 (Pfltiger). Artificially increased pulmonary ventilation does not 

 increase ; and the withdrawal of even half the blood does not 

 diminish the oxygen use. 



Durig has recently put to the most exact test the effect of 

 breathing different percentages of oxygen (11-94 per cent.), and con- 

 firmed the conclusion of previous workers that not the slightest effect 

 on metabolism can be detected. Oxygen inhalation, therefore, 

 cannot be used as a therapeutic agent to increase metabolism. 

 Its only value is to supply sufficient 2 when by reason of anaemia, 

 CO poisoning, nitrite poisoning, &c., the tissues are not adequately 

 supplied. Oxygen cannot do much good to cases of obstructed 

 air-way, for C0 2 has to be got out of, as much as oxygen into, the 

 blood. It can do no good if the circulation is too feeble to keep 

 up the normal rate of supply to the tissues ; there can be little 

 doubt, then, that most of the oxygen inhalations given to patients 

 are useless. The tissues are unable to combine with and store up 

 more than the normal amount of oxygen. Fallaise's experiments 

 show this to be the case. He found that asphyxia produced by 

 breathing H 2 occurred only 45" later than usual after 80 per cent, 

 oxygen had been inhaled by the victim, and this delay was abolished 

 by making the animal breathe air for a minute or two after the 

 inhalation of oxygen. Breathing pure 2 has little effect on the 

 capillary 2 tension, as is seen by the following considerations. 

 There is about 14 per cent. Hb in the blood. Each grm. combines 

 with 1-34 c.c. 2 (Htlfner), and 14 x 1-34= 18-76 per cent. O a 

 when fully saturated. At an alveolar 2 tension of 110 mm. 2 

 the Hb is 81 '5 per cent, saturated that is, the blood contains 

 15'31 per cent. 2 combined ; it also contains 0'3 per cent, 

 simply absorbed, in all 15*61 per cent. On breathing pure 2 



