448 THE RESPIRATION 



logical lobes, the dissolved oxygen will assist in bringing the hemoglobin 

 up to its proper degree of saturation with oxygen. 



It has been imagined by some that it is useless to give oxygen because 

 the dissociation curve of the blood at varying pressures of the gas (page 

 396) shows even after reducing the partial pressure of oxygen to one half 

 that obtaining in normal alveolar air, the blood still takes up 80 per cent 

 of its full load. It is argued that it is therefore futile to attempt to 

 increase the oxygen carried by the blood by raising the partial pressure 

 in the air which is inspired into the still healthy alveoli. From what 

 has been said above, however, it is clear that this viewpoint does not 

 take into account two important effects which follow when the partial 

 pressure of the oxygen is increased, namely, that under this condition 

 oxygen diffuses much more rapidly through the fluid in the pathological 

 portions of the lung, and at the same time that more goes into simple 

 solution in the plasma that is circulating in the healthy portions. 



Principles in Method of Administration. The success of any treat- 

 ment with_Qxygen must depend on several factors, the most important 

 of which are: (1) to get as much of the gas into the alveoli as possible; 

 to start the treatment early before irreparable damage has been done 

 because of anoxemia ; and (87 to maintain the administration until cyanosis 

 disappears. With regard to the first of these factors, it has sometimes 

 been thought that there is an element of danger in giving too much 

 oxygen. This depends on the observations made by several investiga- 

 tors that animals that have been caused to live in more than one atmos- 

 phere of the pure gas for some time develop symptoms of pulmonary 

 irritation, leading on to pneumonia. Even by the best methods of ad- 

 ministration, however, not more than 85 per cent of the gas can be got 

 into the alveoli and it takes three or four days for this percentage to 

 cause pneumonia, even in small animals. (Lorrain Smith.) Karsner 

 has also shown that there is no danger in administration of pure oxygen, 

 even for long periods of time. 



The importance of early administration is evident when we realize 

 that the damage of oxygen deficiency on the nerve centers and the tis- 

 sues usually develops insidiously, and that once started the damage 

 must lead to a progressive deterioration of the vital functions of the 

 body. The respiratory center is among the first to suffer from the anox- 

 emia. The result is shallow and rapid breathing. Such breathing does 

 not, however, properly ventilate the alveoli (page 418), so that the anox- 

 emia becomes aggravated, and a vicious respiratory circle becomes es- 

 tablished. The defensive agencies of the body against toxins and bac- 

 teria are also depressed by the anoxemia so that resistance to the fur- 

 ther progress of the disease is deteriorated. It is also posible that pro- 



