CLIMATE OF CENTRAL AMERICAN PLATEAU. 233 



dren after a stay in the mountains. The ansemia disappeared, while 

 the number of red corpuscles increased. It decreased after return to 

 a lower level, but remained higher than before the sojourn on the 

 mountain. These facts were fully confirmed by the researches of 

 Mercier, von Jaruntowsky and Schroder. 



The greater consumption of oxygen induced by the increase in the 

 number of red corpuscles has been measured. According to Schum- 

 berg and Zuntz, a man brought to an altitude of 12,467 feet consumes 

 33 per cent, more oxygen than at sea-level. The increase is not in- 

 stantaneous. Coindet found that foreigners who had but recently 

 arrived on the Mexican plateau inspired 5.5 liters per minute, while 

 those who had spent a longer period in the same localities took in 

 nearly 6.5 liters. 



But while the adaptive changes take place readily and regularly 

 under ordinary conditions in healthy persons, many observations at 

 health resorts of high altitude have shown that in a few cases (old age, 

 certain organic diseases of the heart) they do not take place at all, 

 while in the case of anannic and neurotic patients they take place only 

 at a moderate altitude and when a cool and bracing atmosphere allows 

 of much outdoor exercise without perspiration. A natural inference 

 to be drawn from those facts is that the climates of all tropical plateaus 

 are not equally conducive to health. While all of them allow life out- 

 doors in any season, and, when not extremely high, are absolutely free 

 from the considerable and sudden changes of temperature which are 

 so injurious to consumptives in the temperate zone, yet the value of 

 such resorts depends mainly on the grade of cooling attending the 

 ascent, especially in the case of general debility, constitutional or even 

 symptomatic. Extremely high altitudes do not agree with the ma- 

 jority of patients; if, at a moderate height (from 3,000 to 5,000 feet), 

 the temperature is low enough to invite exercise, the climate is cer- 

 tainly curative. But if the thermometer reaches daily the eighties, the 

 heart will be unduly quickened during exercise, perspiration will be- 

 come visible, a tired feeling will appear and the hematose as well as 

 the genesis of blood corpuscles will be interfered with. To suffer from 

 the heat while taking exercise is never invigorating, but, in rarefied 

 air, it is an inconvenience which is the more serious in proportion as 

 the altitude at which it manifests itself is greater. It may be said 

 that, other circumstances being equal, the invigorating value of the 

 climate of a tropical plateau depends on the amount of cold bought 

 at the expense of air rarefaction. 



This fact gives the climate of the Central American upland its 

 superiority over that of the broader portion of the plateau which ex- 

 tends from Guatemala to California and which includes the whole 

 Mexican tropical highland. The average yearly temperature of San 



