Page:Encyclopædia Britannica, Ninth Edition, v. 7.djvu/219

201 DIETETICS 201 are strong, but the bones do riot harden in proportion, and if it tries to walk its limbs give way, and it is said to be suffering from rachitis or &quot;rickets.&quot; These consequences follow in other animals as surely as in the human race ; and in them it was possible to make the experiment crucial. A gentleman named Gucrin set himself to find if he could produce rickets at will. He took a number of puppies in equally good condition, and having let them suckle for a time, he suddenly weaned half of them and fed them on raw meat, a fare which at first thought wouldseem the mostsuitable for carnivorous animals. Nevertheless., after a short time, those which continued to take the mother s milk bad grown strong and hearty, whilst those which had been treated with a more substantial dietary pined, and frequently threw up their victuals, then their limbs bent, and at the end of about four months they showed all the symptoms of confirmed rickets. From these experiments we must conclude that the rachitis depended mc%inly on the derangements of nutrition brought on by improper diet. A diet which is taken at a wrong season may fairly be called improper. For carnivora, it is flesh before the age of suckling has passed ; for herbivora (and an experiment bearing on the point has been made on pigs), it is vegetable feeding begun when they ought to be at the teat. 1 The time for weaning should be fixed partly by the child s age, partly by the growth of the teeth. The troubles to which children are subject at this crisis are usually gastric, such as are induced by summer weather: therefore at that season the weaning should be postponed, whereas in winter it should be hurried forward. The first group of teeth nine times out of ten consists of the lower central front teeth, which may appear any time during the sixth and seventh month. The mother may then begin to diminish the number of suckling times ; and by a month she can have reduced them to twice a day, so as to be ready when the second group makes its way through the upper front gums to cut off the supply altogether. The third group, the lateral incisors and first grinders, usually after the first anniversary of birth give notice that solid food can be chewed. But it is prudent to let dairy milk form a con siderable portion of the fare till the eye teeth are cut, which seldom happens till the eighteenth or twentieth month. At this period cltildren are liable to diarrhoea, convulsions, irritation of the brain, rashes, and febrile catarrhs. In such cases it is often advisable to resume a complete milk diet, and sometimes a child s life has been saved by its reapplication to the breast. These means are most feasible when the patient is accustomed to milk ; indeed, if not, the latter expedient is hardly possible. Diet in Childhood and Youth. At this stage of life the diet must obviously be the best, which is a transition from that of infancy to that of adult age. Growth is not completed, but yet entire surrender of every consideration to the claim of growth is not possible, nor indeed desirable. Moreover that abundance of adipose tissue, or reserve new growth, which a baby can bear, is an impediment to the due education of the muscles of the boy or girl. The supply of nutriment needs not to be so con tinuous as before, but at the same time should be more frequent than for the adult. Up to at least fourteen or fifteen years of age the rule should be four meals a day, varied indeed, but nearly equal in nutritive power and in quantity, that is to say, all moderate, all sufficient. The maturity the body then reaches involves a hardening and enlargement of the bones and cartilages, and a strengthening of the digestive organs, which in healthy young persons enables us to dispense with some of the 1 Trousseau, Clinique Medicale, vol. iii. p. 484, 3d edit. watchful care bestowed upon their diet. Three full meals a day are generally sufficient, and the requirements of mental training may be allowed to a certain extent to modify the attention to nutrition which has hitherto been paramount. But it must not be forgotten that the changes in figure and in internal organs are not completed till several years have passed, and that they involve increased growth and demand full supplies. As less bulky food is used, care should be taken that it is sufficiently nutritious, and habits should be acquired which conduce to making the most of it for the maintenance of strength. The nutritiousness of food depends on digestibility and concentration. Food is digestible when it yields readily its constituents to the fluids destined for their reduction to absorbable chyme. It is more or less concentrated, accord ing as a given weight contains more or less matter capable of.supporting life. The degree in which they possess these qualifications united constitutes the absolute nutritive value of alimentary matters. The degree of cohesion in the viands influences digesti bility. Tough articles incapable of &quot; being completely ground up by the teeth, remain unused, while fluids and semifluids lead the van of digestibles. The tissues of young vegetables and young animals are for this reason more digestible than old specimens. It is desirable also that the post mortem rigidity, which lasts several days in most instances, should have merged into softness before the meat is cooked, or should have been anticipated by cooking before the flesh is cold. In warm climates and excep tionally warm weather the latter course is the preferable. The dietician, especially when the feeding of the young is in question, will prefer those methods of culinary prepara tion which most break up the natural cohesion of the viands. And it may be noticed that the force of cohesion acts in all directions, and that it is no advantage for an article to be late rally friable if it remains stringy in a longitudinal direction. Fat interposed between the component parts of food diminishes its digestibility. It is the interstitial fat between the fasciculi of muscular fibre in beef which renders it to young persons and to dyspeptics less digestible than mutton. A temperature above that of the body retards digestion. Meat, which is digested by the gastric juice in the stomach, has time to cool before it gets there ; but farinaceous food, which depends for its conversion into chyme on the salivary glands, suffers a serious loss if by reason of being too hot it cannot avail itself of the saliva supplied by the mouth. It should also be borne in mind that a temperature much above that of the body cracks the enamel of the teeth. Excessive concentration impairs digestibility. The prin cipal medium by which nutriment is carried through the absorbent membrane of the digestive canal is water. There is no doubt it passes more rapidly by endosmosis than anything else. The removal, then, of water is an injury to viands, and drying, salting, over-frying, over-roasting, and even over-boiling renders them less soluble in the digestive juices, and so less nutritious. A familiar illustration of this may be taken from eggs. Let an egg be lightly boiled, poached in water, custarded, or raw, and the stomach even of an invalid can bear it ; but let it be baked in a pudding which requires a hot oven, or boiled hard, or otherwise submitted to a high temperature for a prolonged period, and it becomes a tasteless, leathery substance, which can be of no more use in the stomach than so much skin or hair. It is obvious then that it is mainly in a commercial point of view that articles of diet can be called nutritious in proportion to their concentration. About this there can be no question ; milk adulterated from the pump is worth so much less than pure milk, and a pound of beef steak sustains a man longer than a pint of veal broth. VII. 26