tion of suet, or of more fatty matter, raised it still higher. Dr. Pavy, however, has given an entirely different explanation, and attributes the increase to the action of milk sugar on the disease. It would be an unintelligible exception,' he observes, if the presence of lactin did not render milk an objectionable article of food in diabetes." I feel convinced, nevertheless, for the reason just stated, that lactin, as a constituent of milk, is not converted into diabetic sugar. Indeed such a transformation seems to be effectually prevented by the conversion of the former into lactic acid in the stomach during digestion. Dr. Bence Jones has advanced the opinion that one of the most important physiological uses of lactin is to become converted into lactic acid during digestion, for the purpose of dissolving the albuminous capsules of the milk globules. It is therefore not quite so unintelligible as might be supposed that this substance is not converted into diabetic sugar. It has yet to be determined at what period of the disease the conversion of fat into sugar begins. I am, however, inclined to believe that in its origin it is Op. cit. p. 260. 2 Lectures on Digestion, Respiration, and Secretion: Med. Times and Gazette, April 19, 1851. intermediate between the initial stage characterised by the mal-assimilation of starch and sugar only, and the advanced phase in which albumen also undergoes saccharine transformation. We can thus understand how it is that cod-liver oil has been found to act beneficially, instead of injuriously, when administered sufficiently early in the malady, as in a case recorded by Dr. Bence Jones' and similar instances. At the present time our physiological knowledge relating to the production of sugar from fatty matter is exceedingly limited and unsatisfactory. It is, however, admitted that such a production does take place. Thus Dr. Carpenter2 observes, that it seems also to be established, that compounds presenting a close analogy to sugar may be obtained by the metamorphosis of the oleaginous as well as the albuminous substances within the body.' Some light is undoubtedly thrown on the subject by the researches of certain German physiologists on the fatty origin of glycogen, of which Dr. Carpenter has given the following brief summary: 3 ‘ In addition to the two hypotheses above stated as to the origin of glycogen, a third has recently been put 1 Med. Times and Gazette, Feb. 4, 1854. 2 Principles of Human Physiology, 6th ed. p. 34. forward by V. Deen,' Pogiale, and others, that it is the result of the metamorphosis of fatty substances consumed as food or generated in the liver itself. Küthe and Heynsius especially adopt the latter view, maintaining that the glycogen proceeds from the decomposition of the conjugated biliary acids re-absorbed in the intestine; for in dogs with biliary fistulæ, Küthe found that the liver contained no glycogen and a very small portion (0.2 per cent.) of sugar, whether they had or had not been previously fed with meat; whilst if healthy dogs, after many days' fasting, and in which there should normally have been but a small proportion of glycogen present, were fed with 1 oz. of taurine, and were killed after two or three hours, an abundant supply of glycogen could be obtained from the liver. And again, theoretically, urea and glycogen may very easily be derived from the decomposition of glycine, thus : 2 Eq. of urea 2 (C2 H1 N2 O2)=C4 Hg N4 04 2 2 Eq. of glycogen (C12 H12 O12) =C12 H12 012 4 Eq. of glycine 4 (C4 H5 N 04) C16 H20 N4 016 = : 'And it has already been shown that the quantity of urea rises in diabetes, while the increased size of the liver in this disease is indicative of increased functional activity.' 1 Donder's Archiv. 1860, iii. p. 49. 2 Studien des Physiolog. Inst. zu Amsterdam. There is no fact better established in relation to diabetes than that the albuminous or nitrogenous principles of food become also converted into sugar by the morbid process. The saccharine transformation of albumen, however, unquestionably indicates an advanced stage of the disease. For a time the exclusion of starch and sugar from the food causes the complete disappearance of the sugar from the urine; but as the disease advances, the sugar continues, notwithstanding this restriction, and the exclusive use of a purely nitrogenous food. This has been shewn by Traube, and by Dr. Parkes,' and is demonstrated by common experience. When the disease is so far advanced that this additional source of sugar becomes established, the dependence of the urine sugar on the food is still quite obvious; even when the carbonaceous compounds, starch, sugar, and fat, are excluded from the composition of the latter. It begins to be eliminated in greatly increased quantity shortly after meals, and this augmentation continues for several hours. The amount of sugar formed from the nitrogenous compounds is at first small, but as the disease progresses it becomes more and more abundant. The quantity of albuminous food converted into sugar in 1 Op. cit. p. 348. any given case depends chiefly on the stage and severity of the disease, but to what extent the transformation ultimately attains has not been determined. According to the carefully conducted investigations of Griesinger,' made on a diabetic patient rigorously restricted to a meat diet, the quantity of sugar passed in the urine corresponded to two-fifths of the whole of the meat food taken, or to three-fifths of its contained albumen. From this it will be obvious how little is sometimes left available for the purposes of nutrition. But in the final stage of the disease there can be no doubt that even a larger proportion undergoes mal-assimilation and misappropriation. The extreme degree of emaciation, then, so frequently witnessed in the disease, and the excessive polyphagia with which it is so generally accompanied, are phenomena which are thus fully explained. It seems highly probable that the process of mal-assimilation of starch and sugar determines or originates, as well as increases the intensity, of the saccharine transformation of albumen. Thus Dr. Pavy has reported a case in which, at a time when sugar had for some days been entirely absent from 1 Archiv. für phys. Heilk. 1859, p. 53. |