In fact, then, I write upon an almost unknown and untouched subject.

Lumholtz studied life and customs; my study has been the physical type of south Mexican indians.

Within the area covered by Lumholtz, the physical characteristics of the tribes have been studied by Hrdlicka.

His studies and my own are practically the only investigations within the field.
There are two Mexicos.

Northern Mexico to the latitude of the capital city is a _mestizo_ country; the indians of pure blood within that area occupy limited and circumscribed regions.