are beneficial to the majority of patients. The most important of these can be briefly stated: The number of the blood red corpuscles increases as the air becomes rarer. The main office of the red corpuscles is the absorption of oxygen in the lungs and the carrying of it into the whole body, wherever heat and power are to be generated. There are over two millions red corpuscles 
Noon at the Village Market, Costa Rica. in one drop of the blood of a healthy person. In anæmia and connected states, that number often falls to one half of its value. Life in rarefied air results in the opposite state. After the adaptation period is over, a considerable increase in the number of red corpuscles, coinciding with more frequent and deeper aspirations, causes the paradoxical result, that more oxygen is brought to the organs in the rarefied mountain air than in the denser medium, at sea-level.
The scientist, Viault, was the first to notice that there was an extraordinary number of red corpuscles in the blood of the inhabitants of the high plateaus of Peru. Careful determinations led him to the conclusion that the average increase was from 
Shade and Light Effects at a High Altitude, Carpenteria Mountain. 5,000,000 per cubic millimeter in the blood of a man living at sea-level, to 8,000,000 after a stay of three weeks at an altitude of some eight thousand feet. In their book, La vie sur les hauts plateaux, the Doctors Herrera and Lope, of the city of Mexico, reached a similar conclusion. In Europe, Egger experimented on Monte Rosa (6,201 feet), and found that the red corpuscles increased, on the average, 17 per cent, in two weeks. Karcher, Sutter, Veillon, experimenting on lower altitudes (3,452, 3,232, 2,297 feet), still found a notable increase of the red corpuscles. Wolff and Koeppe noticed it again on the Reyboldsgrun, which is only 2,300 feet high. In 1896, Leuch published in the Korrespondenzblatt f. Schweitzer Aerzte, the results of a most accurate and painstaking study on the changes undergone by the blood of anæmic school chil-
