Of course this is a mere illustration; but the facts I have stated seem to indicate that something of the kind really takes place; and if so, there is no difficulty in understanding the smallness and almost stationary population of the Dyak tribes.
We have next to inquire what is the cause of the small number of births and of living children in a family.

Climate and race may have something to do with this, but a more real and efficient cause seems to me to be the hard labour of the women, and the heavy weights they constantly carry.

A Dyak woman generally spends the whole day in the field, and carries home every night a heavy load of vegetables and firewood, often for several miles, over rough and hilly paths; and not unfrequently has to climb up a rocky mountain by ladders, and over slippery stepping-stones, to an elevation of a thousand feet.

Besides this, she has an hour's work every evening to pound the rice with a heavy wooden stamper, which violently strains every part of the body.

She begins this kind of labour when nine or ten years old, and it never ceases but with the extreme decrepitude of age.