The supply of vitamins to the offspring during gestation and lac tation is ultimately dependent on the diet of the mother so that the provision of a proper diet during these periods is of the greatest importance both for human beings and in the production of milk and meat for human consumption. It is moreover possible that other departures from normality may have a hitherto unsuspected origin in a deficiency of vitamins.
The brief table on p. 221 shows in the most general manner the distribution of the vitamins in some of the common foodstuffs but it must be remembered that the vitamin content of a food is a variable and not a constant quantity. The table clearly indi cates on the one hand how well supplied with vitamins is the nor mal mixed diet and on the other hand how seriously a restricted diet may fail in this respect.
The exact mode of action of the vitamins is still unknown, but both in their effects and in the need which exists for a constant supply of them, they present a striking analogy to the hormones, those chemical messengers, such as adrenaline and secretin, which are elaborated in the body and serve to regulate so many of its functions. The animal is not only entirely dependent on the vegetable kingdom for the organic materials of its nutriment but also for many definite substances (e.g., the amino-acid tryptophan) which are essential for its con
tinued life but which it cannot manufacture for itself. It is not surprising, therefore, that this dependence should be extended to substances even of such fundamental importance as the vitamins. These occur abundantly in the elements of a rational and normal diet and only such diets are capable of maintaining a healthy organism.
.--Medical Research Council: Special Report Series, Bibliography .--Medical Research Council: Special Report Series, No. 38. (revised) Report on the present state of knowledge of Acces sory Food Factors (bibl.) (London, 1924) ; Sherman and Smith, The Vitamins (bibl.) (New York, 1922) ; McCollum and Simmonds, The Newer Knowledge of Nutrition (bibl.) (New York, 3rd Ed. 1925) ; Funk (tr. by Dubin) The Vitamins (bibl.) (Baltimore, 1922) ; Ellis and Macleod, Vital factors of foods, vitamins and nutrition (bibl.) (London, 1923) ; V. G. and R. H. A. Plimmer, Vitamins and the choice of Food (London, 1922) and Food and Health (London, 5928).
(A. HN.)