Heat never seems to trouble them.

Young babies sleep on their mothers' backs without any covering on their heads to protect them from the fierce rays of the summer sun.

On the other hand, the Tarahumare endures cold unflinchingly.

On an icy winter morning, when there are six inches of snow on the ground, many a man may be seen with nothing on but his blanket fastened around his waist, pursuing rabbits.
While their senses are keen, I do not consider them superior to those of any well-endowed white man.

To test eyesight, Sir Francis Galton directs us to cut out a square piece of white paper one and a half inches a side, paste it on a large piece of black paper, and mark how far a person can distinguish whether the square is held straight or diagonally.