The question which follows naturally from a study of the vitamins and their importance in the maintenance of health is how much vitamin-containing food is required in the daily ration? Unfortunately that is a question to which it is impossible to give a categorical answer in the present state of our knowledge. It is generally assumed that one pint of unpasteurized milk a day supplies at least the minimum amount of all three vitamins for a growing child, but it is far from certain that this is the optimum amount. On the contrary experiments already referred to (p. 296) would seem to indicate that a child may be highly benefited by increasing the vitamin content of the food above the customary amount. Still less is known as to the quantitative requirement of adults. A is apparently dispensable after growth ceases, but it is not known with certainty whether the system is actually maintained in perfect health and efficiency over long periods of time on a diet deficient in this factor. It has been shown (p. 179) that the amount of B required may depend upon the character of the diet in respect to protein, fat, and carbohydrate. It is still uncertain what relation exists between muscular activity and vitamin requirement.

It must be continually borne in mind that absence of pronounced disease is not a satisfactory criterion of health. Only when every organ in the body is in a condition of highest efficiency should the individual be regarded as satisfactorily nourished. Malnutrition is probably a much more common condition than we recognize, and we can hardly decide at this stage how far a deficiency in vitamins may be responsible for such condition. On the other hand, so far as we know there is no possibility of overloading the system with vitamins, and it would appear the part of wisdom to so regulate our diet as to ensure the maximum consumption of the vitamin-rich foods. While this is most important in early life it should not be disregarded at any period.

The vitamin content of milk has already been discussed fully. Cream and top-milk may be used as a source of A, and are eminently satisfactory where expense need not be considered too carefully. Skimmed milk retains the antineuritic and antiscorbutic vitamins, but it must be used very liberally if it is to form the sole source of these vitamins. Curran reports that an allowance of one pint of milk per person per day was not sufficient to prevent an outbreak of scurvy in a Dublin work-house when the usual allowance of potatoes was reduced by a potato famine. On the other hand a diet which is poor but not entirely deficient in vitamins can be very conveniently supplemented by the addition of one or two glasses of milk per day.

Butter is a valuable source of A as well as an appetizing form of fat, but unfortunately under present day conditions it is too costly to be used as freely as might be desired. The increasing cost of good dairy butter has led to the substitution of oleomargarine on many tables. Oleomargarine, or margarine as it is called in Europe, is a name applied to any butter substitute made by churning fats other than milk fat with milk. A great variety of fats is used for this purpose, some of them being obtained from animal and others from vegetable sources. Of the animal fats those most commonly used are "oleo oil" and "neutral lard." In the preparation of "oleo oil" beef fat is rendered, clarified, cooled to solidification and separated by hydraulic pressure into the lower-melting oleo oil and the higher-melting oleo-stearine, the latter being used chiefly in the preparation of cooking fats. "Neutral lard " is a carefully prepared lard which is free from taste and odor and is used in the preparation of high-grade oleomargarines. Among the principal vegetable fats used are coconut oil, cotton-seed oil, arachis, or peanut oil, linseed oil, corn oil, and soy (or soya) bean oil.

The use of hydrogenated fats prepared by treating liquid oils with hydrogen in presence of a catalytic agent, has increased rapidly within the last few years. By this means inedible oils such as whale and other fish oils, can be transformed into tasteless, odorless fats of almost any desired melting point. Besides fish oils, soy bean, cotton-seed, rape, peanut, sesame, linseed, and sunflower oils are hardened and used in the manufacture of oleomargarines and lard substitutes. A fat or mixture of fats, of the proper consistency having been obtained, it is churned with milk which has been soured by a pure culture of lactic acid bacilli to give it a pleasant flavor. Butter or cream are sometimes added in varying proportions for the production of the better grades. In some of the European countries the amount of butter-fat introduced is restricted by law, but in the United States any desired amount may be used.

All the experimental evidence goes to show that the fats of the oleomargarines are as digestible and as readily assimilated as butter-fat. The only nutritive superiority of butter lies in its content of the vitamin A. Oleomargarines vary considerably in respect to this factor, according to the fat used in their manufacture. The vegetable fats in general are poor in A and an oleomargarine prepared entirely from such fats will contain only insignificant traces of A from the milk used in churning. Oleo oil is fairly rich in A, although not equal to butter-fat. Animal experimentation has demonstrated that oleomargarines prepared from beef fat will not only serve as adequate source of A for the maintenance of growing animals in normal condition but will restore animals which have suffered decline from deprivation of A. It should, however, be used somewhat more liberally than butter if it is to form the sole source of this vitamin. Lard probably is devoid of vitamin, so that the use of neutral lard does not improve a margarine in this respect. The fish oils are rich in A, but unfortunately this factor is destroyed in the process of hydrogenation.

It may be noted, however, that this does not constitute an objection when the hydro-genated fat is to be used as a lard substitute since, as noted above, the lard itself is presumably vitamin-free.