But these annoyances, great though they be, are very trifles compared to the more serious evils awaiting the traveller in the higher regions of the Cordilleras. At about 12,600 feet above the level of the sea, the effects of the rarefaction of the atmosphere begin to be sensibly and painfully felt. The natives, unacquainted with the real cause of the malady thus occasioned, and which by them is called _puna_, by the Spanish Creoles _veta_ or _mareo_, attribute it to the exhalations of metals, especially of antimony. Horses, not bred in the mountains, suffer greatly from the _veta_, and frequently fall down helpless. The arrieros adopt various cruel means for their revival, such as cutting off their ears and tail, and slitting up their nostrils, the latter being probably the only useful remedy, as it allows the animal to inhale a large volume of air. To preserve them from the _veta_, chopped garlic is put into their nostrils. With human beings, this state of the atmosphere causes the blood to gush from the eyes, nose, and lips, and occasions faintings, blood-spittings, vomitings, and other unpleasant and dangerous symptoms. The sensation somewhat resembles that of sea-sickness, whence the Spanish name of _mareo_. The malady, in its most violent form, sometimes causes death from excessive loss of blood. Of this, Dr Tschudi saw instances. Much depends on the general health and constitution of the persons attacked. The action of the _veta_ is very capricious. Some persons do not experience it on a first visit to the mountains, but suffer on subsequent ones. Another singular circumstance is, that it is much more violent in some places than in others of a greater altitude. This affords ground for a supposition, that other causes, besides the diminished pressure of the atmosphere, concur to occasion it. These as yet remain unknown. The districts in which the _veta_ is felt with the greatest intensity, are for the most part very metallic, and this has given rise to the Indian theory of its cause.