The Fijians: A Study of the Decay of Custom
If all goes well the child is weaned when three or four of both the upper and lower incisors appear. For a month or two before this the mother has been in the habit of giving it a slushy mess of yam to prepare it for solid food. While weaning it she gives it chewed yam or taro in addition to mba, and there is something to be said both for and against this practice. The saliva is rich in ptyalin, which does not act upon proteids or fats, and is therefore not secreted in any appreciable quantity during the first year of infant life. As the starch that is so plentiful in yam and taro is insoluble, it must be converted into something more digestible before it can be assimilated. The acid of the gastric juice would retard this conversion, but the ptyalin of the saliva, like the diastase of malt, has the property of converting moistened starch, when kept at a warm and even temperature such as that of the body, into dextrin and glucose, which are easily as-similated. Thus, while the mother feeds her child upon a diet which it is not yet prepared to deal with, she supplies from her own mouth the necessary moisture, warmth and ptyalin for making it digestible. Without the chewing the mashed yam would produce diarrhœa.
On the other hand, the human mouth is the hotbed of bacteria, which, though innocuous to the adult, may well be hurtful to an infant. The Fijian uses no toothbrush but his index finger, which is seldom as clean as the mouth it is intended to cleanse. It is therefore possible that the fermentative action that causes diarrhœa in children may be set up by the chewing, and the germs of specific constitutional disease may be sometimes introduced. Tuberculosis and leprosy, so far as our present knowledge of them goes, appear likely to be transmissible in this way, and the Fijians are largely affected by both tubercle and leprosy. Most Fijian mothers are heavy smokers, and the residuum of tobacco may well impart a poisonous property to the food.