Precautions.—1. Care should be taken during the testing not to shake the tube or to permit free ebullition. 2. While keeping the contents of the tube hot, the latter should not be held up between the eye and the sky, for then the early color-changes will probably escape observation. The tube should be kept below the eye-level and its contents viewed by the reflected light of some bright object, such as a sheet of white paper propped up an inch or two beyond the tube as a background. 3. Oliver is not aware that the presence of earthy carbonates will prevent the carmine reaction, but as a precautionary measure he suggests the use of a soda-paper whenever the water is exceptionally hard. 4. The acids of the urine rob the carmine-paper of much alkali, so that the addition of more than a certain number of drops of urine—varying of course with the degree of acidity—will at first retard and then prevent the reaction. The addition of the soda-paper will prevent any such interference, although Oliver says that by invariably submitting only one drop of saccharine urine to the test-paper, and keeping up the heating for not less than two minutes, he has never failed to obtain the characteristic reaction without using a soda-paper. It is well to remember, however, that an excessively acid urine may thus interfere, and that the soda-paper will prevent it. 5. The blue color of the carmine is discharged by caustic alkali—liquor potassæ or sodæ. The only chance of being misled by this reaction lies in using an imperfectly cleansed test-tube which may have contained Fehling's solution or the alkaline picric solution. The caustic alkali converts the blue carmine into a green solution, which, on heating, disappears; nor does it return by again shaking the contents of the tube.
Critical comparison of this test with Fehling's solution and picric acid by Oliver has shown that of sixty-four substances experimented upon, normal and abnormal constituents of urine or medicines which after ingestion are eliminated in the urine, Fehling's was reduced by fifteen, picric acid by eleven, and indigo-carmine by eight. The only substances producing the characteristic play of colors with indigo-carmine test-papers reacted with both picric acid and Fehling's solution. They were unoxidized phosphorus, ammonium sulphide, milk-sugar, dextrin, inosit, gallic acid, tannic acid, and iron sulphate. Both the carmine and picric acid were reduced by inosit, which merely turned Fehling's solution green. On the other hand, uric acid and urates, which reduce Fehling's solution, do not react with the carmine test, while kreatinin, which reacts with picric acid also, does not respond to the carmine. Albumen, if abundant, interferes with Fehling, but not with the indigo-carmine.
Detection of Inosit.—It has been said that inosit sometimes accompanies, and even substitutes, grape-sugar in the course of diabetes. It has been mentioned that it does not reduce Fehling's solution, but turns it olive-green. It reduces the carmine and alkaline picric acid solution, and is therefore not recognizable by these. The methods recommended for its recognition in the books are troublesome, and as its presence in the absence of sugar indicates a favorable change, it is not likely that a more precise recognition than is furnished by the olive-green reaction will be needed for clinical purposes.
PROGNOSIS.—The prognosis in diabetes depends upon the organ whose involvement is responsible for the symptoms, upon the stage at which the condition comes under observation, and upon the age of the patient. It has appeared to me that the cases of diabetes depending upon pancreatic disease are the most intractable, that their progress is scarcely checked by treatment, and that they are comparatively rapidly fatal in their termination. In the others, where the symptom is one of a central nervous lesion, it has always seemed to me to be of secondary importance that the glycosuria is itself less marked, that it is unattended by the other distinctive symptoms of diabetes, and that its issue is that of the nervous malady.
Again, it is well known that the later in life diabetes occurs the more amenable it is to treatment, and that if a proper diabetic diet be adhered to by the patient his life need scarcely be shortened. On the other hand, diabetes mellitus is a disease in which the expectant plan is dangerous. If it does not improve it usually gets worse; and many a patient has fallen a victim to his own indifference and indisposition to adhere to a regimen under which he could have lived his natural term of life. This is especially the case when the disease appears after middle life.
If, on the other hand, the condition becomes thoroughly established before twenty-five years of age, it is less amenable to treatment; but even in such cases a promptly vigorous treatment is sometimes followed by recovery. I have already mentioned the case of a child twelve years old in which complete recovery took place.
If tubercular phthisis supervenes, recovery is not to be expected, while intercurrent disease, as pneumonia, which is rather prone to occur, is very much more serious and apt to terminate fatally.
TREATMENT.—The treatment of the aggregate of symptoms known as diabetes mellitus is conveniently divided into the dietetic, the medicinal, and the hygienic, of which the first is by far the most important. The efficiency of this treatment depends upon the successful elimination from the diet of all articles containing grape-sugar, cane-sugar, beetroot-sugar, and starch, it being universally recognized that in the early stages of the disease these foods are the sole source of the glucose in the urine. The normal assimilative action of the liver, by which the carbohydrates are first stored up as glycogen, and then gradually given out as glucose or maltose to be oxidized, being deranged, such foods not only become useless as aliments, but if continued seem to aggravate the glycosuria, and the excretion of sugar steadily increases. There is, therefore, a double reason for excluding them from the food. This is easiest accomplished by an exclusive milk diet. The exclusive milk treatment of diabetes was suggested by A. Scott Donkin in 1868. That he is correct in his assertion that in the early stages of diabetes lactin or sugar of milk is quite assimilable, and does not in the slightest degree contribute to the production of glycosuria, I cannot doubt; that it is in this respect even superior to casein, as claimed by Donkin, I am not prepared to state from actual knowledge; but that casein itself resists the sugar-forming progress immeasurably greater than any other albuminous substance, so that in all but the most sure and advanced or complicated cases its arrest is complete, I am also satisfied. Certain it is that in a large number of diabetics the use of a pure skim-milk regimen results in a total disappearance of the sugar from the urine. That in a certain proportion of these cases a gradual substitution of the articles of a mixed diet may be resumed without a return of the symptoms is also true. In other more confirmed cases the use of skim-milk results in a decided reduction in the amount of sugar, with an abatement of other symptoms, which continues as long as the diet is rigidly observed. In still other cases, while the skim-milk treatment makes a decided impression upon the quantity of sugar, it still remains present in considerable amount, while the disease progresses gradually to an unfavorable issue. These three classes of cases represent, ordinarily, different stages of the disease, so that it may be said that as a rule cases recognized sufficiently early may be successfully treated with skim-milk, although it may occasionally happen that cases pursue a downward course from the very beginning despite all treatment. Yet I have never seen a case which, when taken in hand when a few grains of sugar only to the ounce were present, failed to yield to this treatment.
As to the method of administration, my practice with adults is to give eight ounces (an ordinary tumblerful) every two hours, beginning at seven or eight o'clock in the morning, and continuing to the same hour in the evening. Sometimes it is well to begin with half as much at first, but rapidly to increase to the required amount. This method ensures the ingestion of three to four quarts daily—a quantity generally sufficient to maintain the body-weight of an adult person of average size and taking moderate exercise, although a slight reduction may take place at first. But if the individual is very active or of large size, it will not be found sufficient. In such event the quantity must be increased as demanded by a feeling of unsatisfied hunger. I have known fourteen pints to be taken in twenty-four hours. But when the quantity becomes thus large, the inconvenience in ingesting it is very great, and it is much more convenient to coagulate the casein of a part of the milk and use the curd thus obtained, while the second part is drunk. Curd may be seasoned with salt to make it more palatable, and should be thoroughly masticated before it is swallowed.
The milk should not be taken too cold, especially if the amount ingested is large, else it is likely to reduce the temperature of the stomach below the point necessary for gastric digestion. The temperature should not be less than 60° F., nor much over 100°. Something depends upon the idiosyncrasies of the patient, which must be the guide as to temperatures intermediate between those named.