446 THE RESPIRATION 



carbon monoxide (contained in coal gas) soon become moribund, because 

 the oxygen carrying power of the hemoglobin is entirely abolished by the 

 formation of carboxy hemoglobin. If the animals are now transferred 

 to pure oxygen under two atmospheres pressure (i. e., 10 times the 

 amount in air) they quickly recover. 



Both experiments show clearly that if we succeed in getting sufficient 

 oxygen into simple solution in the plasma, the oxyhemoglobin is not nec- 

 essary to supply the tissues with this gas. 



It is evident, therefore, that oxygen administration can be of no avail 

 in poisoning by coal gas, or any other substance, which destroys the 

 2 -carrying power of hemoglobin, unless it is forced into the alveoli so 

 as greatly to increase the partial pressure.* 



In pulmonary edema, in " gassed" cases, in bronchitis, and in decom- 

 pensated cardiac cases, oxygen is also of undoubted value, when it is 

 properly administered. Many cases of pneumonia are also benefited by 

 such treatment, but there are others in which the heart is so profoundly 

 affected by toxic substances that oxygen may perhaps be of little use. 

 Evidence of this benefit is afforded by the easier and deeper breathing, 

 the slowing of the pulse, the disappearance of cyanosis and the greater 

 ease and comfort experienced by the patient. Not only do these effects 

 persist as long as the gas is given, and thereby serve to tide over a crisis 

 and permit the natural defensive agencies of the body more successfully 

 to combat the abnormal condition, but they often outlast the administra- 

 tion. 



Quantitative evidence that in pneumonia the arterial blood is improp- 

 erly saturated with oxygen in proportion to the degree of cyanosis, and 

 therefore of the condition of the patient, has been furnished by Stadie. 68 

 In a normal person the arterial blood carries 95 per cent of its full load 

 of oxygen, but in pneumonia only a little over 80 per cent. Meakins 72 

 has confirmed these findings, and has added most important observations 

 on the effect of oxygen inhalations by the Haldane method. In a case 

 of pneumonia the oxygen unsaturation on the eighth day of the disease 

 was 17.9 per cent. After two hours of oxygen treatment (at a rate of 

 delivery of 2.5 liters 2 per minute) the unsaturation percentage fell 

 to 9.08, and after 18 hours (at 1 liter per minute) it was 9.0. The 

 2 was then discontinued and in 4 hours the unsaturation percentage 

 had risen to 15.5. It fell subsequently to 3.05 after 24 hours, during 

 which 3 liters 2 per minute was administered. Shortly after this the 

 crisis occurred. Similar results were obtained in a case of chronic bron- 

 chitis, and even in normal men it was found that inspiration of 3 liters 



'Hemoglobin becomes converted into methemoglobin and incapable of carrying labile O 2 in vari- 

 ous types of poisoning, e. g., acetanilide, nitrobenzol. 



