Fat may be given in Diabetes, for it is not proved that it can be converted into sugar; but as the contrary seems to be the case with albumen, and it being impossible to withhold this, the cure of the patient by mere dieting may be considered almost hopeless. We have seen that Starchy and saccharine matters form an important element of the food; and that, by combining in the blood with the Oxygen absorbed in the respiratory process, they are of use in maintaining the heat of the body. In some constitutions there is a peculiar tendency to an abnormal oxidation of these materials into Oxalic acid. It appears likely that Cane-sugar is more liable to this change than Grape-sugar, although it may occur with the latter. Thus the patient is sometimes benefited by an injunction to abstain entirely from this article of food. Fatty matters need not be given where there is organic disease of the Pancreas; as in that case they are not rightly digested. This is a rare case. They are sometimes repugnant to the stomach, from other causes. The application of oily substances to the cure of Phthisis is a matter of considerable importance. Of late years Cod-liver oil has been used with more success than any other medicine, both as a prophylactic, and as a curative agent in this disease. When this remedy is considered separately in Chap. IV., mention will be made of several theories which have been propounded to account for its mode of operation. Liebig's idea that there is in Phthisis an excess of Oxygen in the system, would, if sufficiently supported, serve to explain its action when considered simply as oil. This Oxygen would consume the Carbon and Hydrogen in the food, and prevent the accumulation of fat. (_Liebig's Animal Chemistry_, part i. p. 126.) A supply of oil might then serve to restore this fat, and afford a sufficient pabulum to the devouring element. Thus an attention to diet is of great importance in the cure and alleviation of different diseases; for by this means we are enabled, within a certain limit, to regulate and control the composition of the blood, and through it the nutrition of the body. Thus are Aliments essentially Restorative, forming and supplying the blood, and from it the several tissues, which are destined to work and to endure, until, like all organic creations, their turn is come to die. Then only are they excreted, and in a different form from that in which they entered; at that time, developing into tissues of high organization, they now decompose and retrograde into simpler bodies; at first fitted for life, they are now shaping for destruction. The disease which collectively they are intended to cure is Hunger; which is in fact a call from the blood for the renovation of its failing constituents, a demand for fresh supply from the body, which, because always changing, is always requiring nutriment. ORD. II. ACIDS.