450 THE METABOLIC PROCESSES OF THE BODY. 



388. A temporary diabetes may he brought about by the administra- 

 tion of the substance phloridzin. This, however, is a glucoside, and part 

 of the sugar which appears in the urine, after a dose of it, may come direct 

 from the drug itself; but the quantity of sugar discharged is too great to 

 be accounted for in this way, and similar diabetic effects are produced by 

 the administration of phloretin, a derivate of phloridzin, not a glucoside, 

 and not giving rise to sugar by its own decomposition. The sugar which 

 appears in the urine after a dose of this substance seems to come in part 

 at least from the hepatic store of glycogen when that is present ; but the 

 drug will give rise to sugar in the urine of starving animals, from whose 

 livers (and other tissues) glycogen is presumably absent. 



Artificial diabetes is also a prominent symptom of urari poisoning. This 

 is not due to the artificial respiration, which is had recourse to in order to 

 keep the urarized animals alive ; because, though disturbance of the respir- 

 atory functions sufficient to interfere with the hepatic circulation may pro- 

 duce sugar in the urine, artificial respiration may with care be carried on 

 without any sugar making its appearance. Moreover, urari causes diabetes 

 in frogs, although in these animals respiration can be satisfactorily carried 

 on without any pulmonary respiratory movements. The exact way in 

 which this form of diabetes is brought about has not yet been clearly made 

 out. 



A very similar diabetes is seen in carbonic-oxide poisoning ; and is one 

 of the results of a sufficient dose of morphia, of amyl nitrite and of some 

 other drugs. 



There can be no doubt that in diabetes, arising from whatever cause, 

 the sugar appears in the urine because the blood contains more sugar than 

 usual. The system can only dispose (either by oxidation, or as seems more 

 probable in other ways) of a certain quantity of sugar in a certain time. 

 Sugar injected into the jugular vein reappears in the urine whenever the 

 injection becomes so rapid that the percentage of sugar in the blood reaches 

 a certain (low) limit. Sugar in the urine means an excess of sugar in the 

 blood. How in natural diabetes that excess arises has not at present been 

 clearly made out. It may be that some forms of diabetes resemble the 

 artificial diabetes just described as resulting from puncture of the medulla, 

 and arise from a too rapid conversion of the hepatic glycogen, or from 

 carbohydrate material failing to be stored up as glycogen, or from an 

 excessive manufacture of carbohydrate material by the hepatic cells. All 

 forms of diabetes, however, cannot be satisfactorily explained in this way ; 

 and it has been suggested, though adequate proof has not yet been supplied, 

 that the sugar of diabetes is of a peculiar nature and accumulates in the 

 blood because it is unable to undergo those changes, whatever they be, 

 which befall the normal sugar of the blood. We cannot here discuss the 

 subject in detail ; but there is much to be said in favor of the view that the 

 sources of the excess of sugar in the blood may be various, and hence that 

 several distinct varieties of diabetes may exist. In severe cases of diabetes 

 the aberrant nature of the metabolism which is going on in some or other 

 of the tissues of the body is shown by the appearance of abnormal sub- 

 stances in the urine. Thus acetone is frequently present, and the fatal issue 

 of certain cases has been attributed to poisoning by that substance ; oxybu- 

 tyric acid and other various organic, chiefly volatile, acids are also some- 

 times present. But in respect to these and other abnormal bodies we are 

 not at present clear whether they are, like the sugar itself, the products of 

 an abnormal metabolism which is the root of the disease, or whether they 

 are secondary products, that is to say, products of the general disordered 

 metabolism induced by the constant presence in the blood of an excess of 



