By this time it will have become apparent to the reader why rickets is common in those parts of the world where milled cereal products, tubers and muscle meats form the principal components of the dietary. Such a diet has repeatedly been shown to be inadequate for the production of satisfactory milk by a lactating mother. When we consider also that the manufacture and use of proprietary infant foods, most of which contain large proportions of cereal products, has grown to vast proportions, and that the practice of introducing very early cereals into the diet of infants, with a consequent displacement of milk, is all but universal in recent times, it is easy to understand how rickets would be expected to be common. In fact, the successful feeding of a young omnivorous animal during infancy and adolescence is a very difficult matter with which to succeed well. Young carnivora in a wild state eat glandular organs and chew soft bones as soon as they take their first steps in independence of the mother's milk, and under these conditions do not develop skeletal abnormalities. When kept in confinement and fed upon muscle meat, body fat, and a bone so large and hard that little can be gnawed from it, they invariably develop rickets (23). Young carnivora are now successfully reared in a few places by supplying them with liver, flat bones containing much red marrow, fat, and at intervals of a few days with small birds or mammals which they can entirely consume. Confinement does not seriously interfere with the development of young lions under such conditions of feeding.

Young herbivora, on the other hand, begin very early to eat tender leaves of grass, and long before they have been deprived of their milk supply have become consumers of large amounts of forage plants. This type of diet suffices for the normal development of the skeleton.

It is very different with the human infant, and with certain domestic animals which are fed an omnivorous type of diet. The human infant is nursed by a mother whose diet tends to be limited to the milled cereal, tuber and muscle meat type but with just enough milk, cream, and green vegetables to prevent the development of spectacular breakdown in her nutritional processes. Her milk is defective in some degree. The nursing period of the infant is frequently shortened for the sake of the interest of a poorly nourished mother. Milk which is fed as a substitute for breast-feeding is usually modified by dilution and the addition of cereal water, or proprietary foods having a cereal basis. There can be no question that the modern practice of modifying milks for infant feeding represents one of the most gigantic and tragic examples of persistent blundering of which civilized man is guilty. Fortunately the time seems near at hand when any manipulations to which cow's milk is subjected for feeding infants will be carried out with knowledge of what is being done, and the mistake of concocting mixtures which are entirely unsuited for the nutrition of the growing child be avoided.

344. Suggestion Of Cause Of Occurrence Of Rickets In Dogs But Not In Cats

Young dogs which are fed essentially the same food that man is now subsisting upon in Europe and America are prone to develop rickets, whereas cats, because of their tendency to prowl about in search of birds, rodents and other small creatures, which they destroy in large numbers, escape the disease. Their diet remains similar to that of wild carnivora, because they cannot be domesticated sufficiently to lead them to discontinue the practice of hunting. The dog adapts himself much more readily to domestication, and accepts his food from his master. In many instances this does not now prove satisfactory for the promotion of normal growth in the skeleton, and rickets is, therefore, of frequent occurrence.

345. Why Are The Eskimos And Lapps Free From Rickets

The Eskimo, the Icelanders and the Lapps are free from the disease, or were until contact with the world through commerce changed the dietary habits of some of them. The changes which have in certain instances brought about the appearance of rickets, represent essentially the substitution of a considerable amount of milled cereal products, molasses, syrup, legume seeds and canned seed products, for a part of their primitive kinds of foods. In their primitive condition these were all essentially carnivorous in their dietary habits.

346. Rickets Rare In Iceland

Iceland was settled in the ninth century by colonists from Ireland and from Scandinavia. They took with them cattle and sheep, and soon developed a considerable animal industry which flourishes today. Agriculture did not yield a return for labor, and accordingly the people of the island subsisted for generations essentially upon milk, mutton, fish, birds' eggs at certain periods of the year, and wildfowl. Under such living conditions they remained a vigorous people, but they have suffered from deterioration of the teeth during the last seventy-five years. It is during this period that they have engaged most extensively in commerce. Parallel with the exportation of their local products and the importation of cereals and other foods of the type which have come to compose so large a part of the diet of the urban population of Europe and America in recent decades, they have become more and more afflicted with dental caries. Stefansson (24) secured 96 skulls from a cemetery in Iceland dating from the ninth to the thirteenth centuries, and presented them to the Peabody museum of Harvard University. These have been described by Hooton (25), who found no certain evidence of caries in any of the teeth. Several teeth were broken but none were decayed. The teeth of the Lapps are essentially perfect as are those of the Eskimo in their primitive condition on a carnivorous diet.