400 THE RESPIRATION 



sickness have been given elsewhere in this volume (page 360), where the 

 general symptoms are also described. In this place we shall consider 

 very briefly some of the more general aspects of tlic condition, and, more 

 particularly, the nature of the adaptation that occurs. All of the symp- 

 toms are essentialy dependent upon lack of oxygen. Cyanosis is com- 

 mon and the symptoms are much the same as those of coal-gas poisoning. 

 Not only does this deficiency of oxygen cause acid substances to appear 

 in the blood, thus raising the C H and stimulating the respiratory center, 

 but it allows other poisonous materials to accumulate. These act on the 

 various nerve centers, producing symptoms which vary in different in- 

 dividuals according to their relative susceptibilities. In some, the diges- 

 tive centers are affected and nausea and vomiting occur; in others, the 

 higher cerebral centers are affected, causing depression and general men- 

 tal apathy, great drowsiness, muscular weakness, or it may be mental 

 excitement and loss of self-control. 



The susceptibility of different individuals also varies according to the 

 amount of previous experience in mountaineering and the type of breath- 

 ing. Much of the value of previous experience and training depends on 

 the ability to perform muscular effort economically; to adjust the effort 

 to the available oxygen supply without permitting unoxidized harmful 

 products to accumulate in the body. It often happens that no symptoms 

 appear so long as the person is at rest, but immediately do so whenever 

 any muscular effort demands a much more abundant oxygen supply. 



The type of breathing that best withstands the rarefied air is slow and 

 deep, rather than rapid and shallow. The reason for this is of course 

 that much more of the outside oxygen gets into the alveoli in the former 

 case than in the latter, the dead space being practically constant. The 

 following figures taken from observations on three different individuals 

 will illustrate the importance of this factor. 



(From Halliburton.) 



After living for some time in the rarefied air and quite independently 

 of training in the efficient performance of muscular work, adaptation 

 occurs, so that the symptoms pass off. The essential feature of this adap- 

 tation is increased absorption of 2 into the blood. Three mechanisms 

 have been described as responsible for this effect: (1) increase in the ten- 

 sion of 2 in the alveolar air; (2) assumption by the pulmonary epithelium 



