But we now know (and many, indeed, have recognized it for many years) that the nutrition of the animal body, and especially of man's body, is not so simple a matter as this method would suppose. It is necessary not merely to supply the proteids, fats, starches, and sugars, in correct weight and bulk, but also certain qualities and substances in food, much more subtle and difficult to estimate precisely, which are required in order to maintain health. There are elaborate chemical compounds present in really "fresh" meats and vegetables which seem to be absolutely necessary in order to keep man (and some of the higher animals) in health, and not only that, but it is ascertained that without them he cannot be properly nourished, but dies! These subtle, highly complex bodies seem to be present in very small quantities in good fresh food, and yet are absolutely necessary though so minute in amount. The failure of a diet consisting exclusively of tinned meats and preserved foods is due as much to this as to the nausea set up by it—of which I have written on a former occasion ("Science from an Easy Chair," Second Series, 1913, p. 171, "Food and Cookery").
Let us take an example. A distinguished medical chemist, Mr. Gowland Hopkins, has recently published an account of some experiments in which he fed young rats on a purely chemical, or "artificial" diet. He gave them, in proper proportions, chemically purified casein or curd, starch, sugar, lard, and salts, mixed into a thin paste with water, of which they had an abundant separate supply. Young rats fed with abundant natural foods of mixed substances, such as cheese, bread, egg, bits of meat and vegetable, and water, grow rapidly; they double their weight in twenty days. The young rats fed by Mr. Hopkins upon the artificial pure food—though supplied with it and taking it in abundance—did not increase in weight, and most of them died before the twentieth day! The curious and important fact was established (by careful and repeated experiment) that if a teaspoonful of milk was added to the artificial food (less than one twenty-fifth of the solid matter of their daily food) the young rats did as well as on "natural" food, doubled their weight in twenty days, and grew up to be strong and healthy rats. It was made clear that something was obtained by the rats from the small quantity of milk—something necessary for carrying on their nutrition, something the importance of which was not its quantity but its peculiar quality, which was absent in the artificial diet, but present in the mixed diet of varied materials which a young rat naturally gets. It seems that some highly elaborated proteid is necessary, if only in minute quantity, to set nutrition going, and that this is furnished by the teaspoonful of milk. Here, then, we have a case in which the simple rough conclusions as to all that is necessary in diet being the proper quantities of flesh-forming and heat-giving substance, are found to be erroneous.
Take another case—that of the disease known as "scurvy." The word "scurvy" means "afflicted with scurf, mean and dirty." It was applied to persons afflicted by this particular disease, and a Latin medical word, "Scorbutus," was made from it in the Middle Ages, which survives as "scorbutic" at the present day. Scurvy was formerly very common on board ship, in beleaguered armies, in prisons, and in other conditions in which men's food was limited to dried and salted, often badly preserved, meat and biscuit, or stale bread. Its real causation is not even now agreed upon: some holding that it was due to actual poisoning by the badly preserved food, others that it was due to the absence of certain elements—only to be obtained from fresh meat or fresh vegetables. Others think that it was caused by a bacterium. The victim of scurvy becomes much debilitated, the gums become spongy and ulcerated, and extravasations of blood are found in all parts of the body, often leading to ulceration. In the old times a whole ship's crew of the Navy would be attacked by it, and half or more died before a port could be reached and fresh food obtained. It was found that the use of fresh vegetables, fresh meat, and the juice of fruits prevented its outbreak, and cured it when once started. For one hundred and fifty years it has been held in check by the use of lime-juice as a drink whenever supplies of fresh vegetables and meat run short. It has now become so unusual a disease that there has been no proper study of it in the light of modern knowledge.
It seems to be essentially the same condition of malnutrition as that which prevailed in cities and large tracts of country in the Middle Ages and occurs at the present day in Norway, caused by a diet of badly salted fish and dried meat. This produced ulceration of the extremities, allowing the leprosy bacillus to make its way through the broken skin into the tissues, and thus led to the widespread occurrence of leprosy. Whether bacilli of any kind were concerned in the old virulent outbreaks of "scurvy" on sailing ships must remain uncertain, but it is highly probable that they were. In any case, it is certain that the juice of fresh meat or of fresh vegetables when taken set going a better condition of nutrition in the body, and so acted as a preventive and a cure of scurvy. Some writers suppose that it was the salts, such as citrates and lactates, present in fresh fruits and vegetables which were effective in staying the disease; but this has by no means been proved, and is not, at the moment, accepted. It is probable that here, as in the case of Mr. Hopkins's rats, it was a quite minute quantity of a readily-destroyed proteid present in fresh meat and vegetables which was necessary to keep the chemical processes of nutrition in healthy activity.
This view is supported by the fact that in recent years a disease of infants similar to scurvy, and called "infantile scurvy," has been described by Sir Thomas Barlow, and fully recognized. It is a condition of "malnutrition," and is accompanied by "rickets," and is due in the first place to failure of the mother's milk, and secondly to the bad quality of the cows' milk substituted for it. Owing to the danger of infection by bovine tubercle-bacillus and the great expense of "certified" milk from specially selected cows (eightpence a quart), it is customary to boil the milk given to children. There seems to be no doubt that good milk, freshly boiled, is satisfactory. But the constant use of sterilized milk and so-called Pasteurized milk, as well as inferior "watered" and more or less stale milk, is frequently the cause of infantile scurvy. Something is destroyed in the milk by prolonged heating which is necessary for its proper action as a food. The addition to the milk of a small quantity of fresh meat-juice or beetroot-juice appears to replace this destroyed matter, and to prevent malnutrition and scurvy. And thus the babies are rescued from "infantile scurvy." Here, again, it is a question of the presence of a minimal quantity of an easily destroyed proteid, which is necessary to start the nutritional process and to keep it going.
A very interesting case of the unsuspected influence of minute quantities of such a "proteid" body (that is, a body like casein and albumen, but higher in the complexity of its chemical structure and nearer to the readily destroyed chemical complexity of living matter itself) has lately been discovered. In the East, especially amongst Chinese "coolies" and other people who feed on rice, a very troublesome disease is known, called "Berri-berri." It is chiefly marked by pains all over the body, lassitude, and debility, and renders its victims unfit for labour, and so causes great inconvenience to employers of "Chinese cheap labour." All sorts of causes have been suggested for it. But it has now been found that it is due to the feeding of the coolies with "polished rice." This is an inferior rice, the grains of which have become (by bad, damp storage) rough and powdery on the surface. The bad rice grain is purchased by dealers and shaken up and sifted so as to get rid of this dull surface, and is then known as "polished rice." The grain has lost its outer coat. It has been found that domesticated birds (pigeons and fowls) fed on this polished rice become ill with symptoms like those of "Berri-berri," and even die. And it has been further discovered that these same birds can be cured by mixing some of the separated outer coat of sound rice grains with the "polished rice." The result of this observation on birds has been applied to human patients suffering from "Berri-berri." It is found that they are rapidly cured by giving them rice "outsides" to eat, and that those who are feeding on "polished rice" can be prevented from acquiring the disease "Berri-berri" by mixing rice "outsides" with the polished rice. The study of the subject has gone further.
A crystallizable substance allied to proteids has been separated by the chemist in quite minute quantity (one part by weight in 10,000 parts of rice) from the outer coat of rice grain, and is called "vitamine." It is this substance which prevents the "whole" rice grain from causing "Berri-berri" in men and birds who feed on it, and it has been shown experimentally that it prevents the development of "Berri-berri" when taken with "polished rice," and cures it when administered to man or bird suffering from that disease. This case calls to mind the popular notion that the indigestion caused by eating a "peeled" raw cucumber can be prevented by eating some of the dark-green "rind" or outside of the cucumber. I do not know that anyone has ever shown that this is a true doctrine, but it serves as an illustration of what has been demonstrated in the case of rice grains and "Berri-berri." Here, then, again we have, in the case of rice, a minute quantity of a substance naturally present in an article of food when taken in its natural normal condition, which is destroyed and removed by the ignorant manipulation of man, although necessary and essential if that article of food is to serve as healthy diet. In this case (as so many others) it is the attempt of greedy traders to make money by giving to a worthless spoilt article the appearance of the regular and valuable article, which has led to disease and disaster. It becomes more and more obvious that the selection of articles of food and the whole question of what is a healthy diet, are not such simple things as is often supposed. Here, as in everything we do, we must either keep to the long-established habits sanctioned by Nature, or we must have full and detailed knowledge to guide us in new ways, so that we shall not recklessly blunder by ignorance into disaster and death. The "feeding" of man and of his herds requires new and continued investigation. Old convictions and traditions in these matters must not be lightly thrust aside by the possessor of that little knowledge which is a dangerous thing. Meanwhile, for the civilized man the advice of Pasteur's pupil and successor, the late Professor Duclaux, is noteworthy: "Do not eat much, but eat many things; there is safety in variety, danger in uniformity."
When we reflect on the importance of these small quantities of easily destroyed constituents in natural foods, we begin to appreciate the difficulty of securing a pure milk-supply which shall be at the same time a nourishing and a healthy one. The sterilizing of milk by heat before it is sold as an article of diet seems to be desirable in order to destroy the bovine tubercle-bacillus which may be there and the other injurious microbes due to the dirty conditions in which the cow is kept and the milkers keep themselves. The heating of the milk for some twenty minutes to a temperature below that of boiling water seems to be the best plan. For infants, meat-juice or beet-juice may then be added to the milk when used, and so "infantile scurvy" be avoided. Consumers (older children and adults) who are taking other foods do not need this additional precaution. Milk thus "Pasteurized" is the safest milk.
But there is a very serious precaution to be observed in all cases. In such Pasteurized milk the lactic organism or ferment usually present is destroyed. Consequently the milk does not "go sour" by the growth of the lactic ferment. This is no advantage, but a serious danger. For the lactic "souring" of milk is not injurious, but, on the contrary, a safeguard. It actually prevents the growth in the milk of other really harmful and deadly germs. Thus when the lactic germ is not there, but killed by heat, these other deadly germs get their chance. A fly or other dirt-carrier brings to the sterilized milk "putrefactive" bacteria and such germs (terribly common) as those of "green" or infantile diarrhœa, not to mention others. If the milk had been unsterilized and gone sour by the growth of the lactic ferment, these more dangerous germs could not have flourished in the acid conditions produced by it. The danger of Pasteurized milk is that if kept more than a few hours at the ordinary temperature of a dwelling-room, and not carefully protected, it may be a very ready means of communicating infantile diarrhœa and other intestinal disease. It would therefore seem to be desirable to restore to the Pasteurized milk a small quantity of a pure culture of lactic germs. This could be easily done. The milk would have had its tubercle-bacilli and others removed by heat, and then, after cooling, it would receive a very few lactic germs as a protective in case it should be kept by the consumer long enough to get infected by the bacteria of intestinal disease. It is imperative that good, nourishing milk, free from germs of tubercle and of diarrhœa, shall be accessible to the millions in this country who cannot afford to pay eightpence a quart for it. It is a difficult demand to meet. What is said above explains the difficulty, and suggests an attempt to overcome it.