374 TRAVELS AMONGST TEE GREAT ANDES, chap. xix. 



prolonged diminution in pressure, the fact must affect all calcula- 

 tions which may be made on the basis of higher pressures either 

 in respect to the marching of troops, transport by animals, the 

 labour of the navvy, or any other description of work dependent 

 upon muscular exertion. 



In reviewing the whole of our experiences, two different sets 

 of effects could be distinguished ; namely, those which were 

 transitory, and those which were permanent, — that is to say, 

 permanent so long as we remained at low pressures. 



The transitory effects were acceleration of the circulation of 

 the blood, increase in the temperature of the body, and pressure on 

 the blood-vessels. The permanent ones were augmentation of the 

 rate of breathing and disturbance of the habitual manner of 

 respiration, indisposition to take food, and lessening of muscular 

 power. The whole of these, doubtless, were due to diminution 

 in pressure, but the transitory ones, presumably, ivere produced hy 

 some cause which was itself only temporary} There are strong 

 grounds for believing that they are due to the expansion (under 

 diminution of external pressure) of gaseous matter within the body ; 

 which seeks to be liberated, and causes an internal pressure that 

 strongly affects the blood-vessels. While equilibrium was being 

 restored between the internal and external pressure, the ' indescrib- 

 able feeling of illness ^ gradually disappeared, and headache died 

 away ; and it may be reasonably expected that these ^ acute ' 

 troubles can be escaped by taking pains to avoid abrupt diminution 

 of pressure.* 



^ During the whole time we were in Ecuador, neither with ourselves nor among 

 the people who were employed, was there anything observed of the nature of 

 hemorrhage, vomiting, or nausea (although among our viandes there was something 

 that would have strained the stomach of an ostrich [see pp. 61 and 207]) ; and it 

 thus appears that these unpleasant features are not indispensable accompaniments 

 of life at great elevations. 



2 Or, on the contrary, suffocation may be expected, probably accompanied by 

 hemorrhage, by persons who submit themselves to a very rapid reduction in press- 

 ure (either in balloon, or artificially), if they have previously been living for some 

 length of time with the barometer at 29 to 30 inches. 



i 



