378 THE RESPIRATION 



matic Chamber. These have been carefully described by Haldane, Kellas 

 and Kennaway, 59 who exposed themselves and others to 380 mm. baro- 

 metric pressure (corresponding to about 19,000 feet above sea level) for 

 at least an hour on several successive days, the pressure being. lowered to 

 this level very quickly (5 minutes). The symptoms varied somewhat in 

 the different subjects. The respirations increased in depth and frequency 

 at first but then returned more or less to normal in four out of six of the 

 observed persons. In one it remained very rapid, and in another it readily 

 became periodic subsequent to holding the breath for a time. The pulse 

 always increased at first and then returned almost to normal. Cyanosis 

 was always present but did not diminish with continued exposure. Al- 

 though mental and sensory symptoms were not perceived, the sudden raising 

 of the oxygen percentage caused the light to become brighter and sounds 

 to become louder. Vigorous muscular work caused marked hyperpnea, 

 quick pulse, increased cyanosis and mental confusion. There were none 

 of the symptoms of mountain sickness (page 415) and no ill-effects were 

 experienced on leaving the chamber. 



At still lower pressures the above mentioned changes in pulse and respira- 

 tions became much more pronounced and decided mental symptoms ap- 

 peared, for example it became very difficult to count the pulse, or to 

 record the other observations. Loss of memory was common, but there was 

 no loss of consciousness. A most interesting mental symptom sometimes 

 observed was fixedness of ideas. This has also been noted in coal gas poison- 

 ing, and in high balloon ascensions. Thus, in one experiment the sub- 

 ject persisted in having the pressure held at a certain (very low) level 

 for no evident reason, just as those exposed to carbon monoxide can not 

 be diverted from remaining exposed to the gas. 



These symptoms have been described in some detail since it is im- 

 portant that they be compared with those in clinical cases in which 

 oxygen deficiency exists. They constitute the reactions of healthy in- 

 dividuals to conditions which may become established as a result of 

 disease, and it is obviously most important in such cases that they be 

 distinguished from the more definitely pathological symptoms. 



On comparing the above symptoms to those of mountain sickness it 

 will be noted that there is a marked difference (see page 415). One pe- 

 culiarity of the latter condition is that prolonged stay in the rarefied air 

 brings about an acclimatization, so that after some days the person is 

 practically normal. The attempt was made in the above experiments 

 to bring about a similar acclimatization with partial success. 



The Nature of the Changes Produced in the Body in Anoxemia. A 

 careful study of this aspect of the problem is most important, not only 

 because it throws much light on the manner of control of the respiratory 



