If the mother's diet, though containing a sufficiency of protein, contains these in a form which is not fully adequate for promoting growth in the offspring, the maternal organism supplies the foetus with what is lacking by drawing upon the maternal tissues.

The amount of supplementary protein required to make good the inadequacies of the proteins of such foods as corn, cereals, seed, bananas, carrots, etc., is very small. It is much less than would be required if the supplementary food were the sole scarce of protein. Mothers whose diet is largely cereal require some supplementary protein, but not large quantities of this.