Santa Cruz, Trinidad, and Yungas mark the regions of a continuous tropical summer, where the rains are more frequent and copious and where the earth yields her fruits in astonishing richness.
While the wet season of this part continues from November to April, rains, though less frequent and abundant, occur during the remaining months. By reason of the annual inundation of large areas of this region and the continuous hot climate and consequent noxious exhalations from the decaying vegetation, malarial fevers and other diseases common to warm climates are prevalent. This is more especially true of the extensive tropical provinces of the department of Beni, though, unlike the fevers of the malarial districts of Colombia and Brazil, they yield to simple treatment, while the epidemic maladies which occur here from time to time are not of a violent character.
Along the narrow valleys of the Mapiri and Tipuani rivers, where the purifying currents of fresh air are, in a measure, obstructed by abrupt and elevated mountain walls, a tertian fever prevails, called terciana, an intermittent, whose paroxysms occur about every forty-eight hours.
In the absence of proper medical treatment, a large percentage of the mortality occurring among the Indians of these and other low valleys of Bolivia result from this disease. Strangers entering these sections, and especially Mapiri and Tipuani, should be amply supplied with quinine, and carefully avoid freshly plucked fruits and alcoholic drinks.
The regions above 13,000 to 13,500 feet are, as a rule, too cold for habitation, and the vegetation is correspondingly scant, being limited to hardy grasses and mosses and stunted shrubs, with here and there small patches of barley, potatoes, and quinia.
The snow line of the Cordilleras varies from 15,000 to 18,000 feet, "modified in many cases by the aspect of the mountains and the nature of the country surrounding them." The main Cor-
