The most important symptoms of a typical case of diabetes which are to be combated by diet are (a) extreme thirst, (b) the large quantity of urine voided and rapid emaciation and loss of strength.

(A) Thirst. The Mouth

Thirst becomes excessive, and is not quenched by drinking, although patients will drink almost any available fluid - even their own urine - in their endeavour to relieve it.

The absorption by the blood vessels of fluid from the tissues is held to be the main cause of this thirst (Vogel), which is most intense one or two hours after meals, when sugar formation is most active, and ten or fifteen quarts of water may be consumed daily if patients are not restrained from drinking freely.

The saliva is thick, frothy, and acid, and often contains sugar.

The mouth becomes sticky or dry, even to the extent of interfering with articulation, and there is often a sweetish taste, which may be accounted for by the sugar present in the saliva and the blood of the capillaries which circulate among the taste bulbs.

The tongue is at first moist and sticky and coated with prominent papillae; later it may become dry, dark red, and fissured. The appetite is at first excessive; it amounts to bulimia in some cases; at other times it is capricious or intermittent, and subsequently it fails completely when the digestion becomes impaired through the symptoms of gastric and intestinal catarrh.

(B) The Urine

The average quantity of urine voided is between two to three times the normal amount - that is, from 3,000 to 4,500 cubic centimetres. If water is being drained from the tissues the quantity of urine voided may exceed the amount of fluid ingested, but obviously this condition cannot last very long. Exceptionally as much as 5,000 to 6,000 cubic centimetres or more may be voided within twenty-four hours.

Frequent calls to micturate at night greatly interfere with the patient's rest. As a rule, the more sugar present the paler is the urine, and it grows turbid soon after standing, from the development of yeast fungus (Torula cerevisia), derived from the atmosphere. The sediment, if present, is usually light, and the odour may resemble whey or hay. The urine is sweetish; the reaction is usually acid, but may be neutral or alkaline, and the acidity is usually proportionate to the quantity of sugar; it is increased by development of carbon dioxide and acetic acid, products of fermentation. After standing it does not become alkaline from ammoniacal fermentation, but undergoes saccharine fermentation. In a majority of cases the specific gravity is considerably higher than the normal, rising to between 1.035 and I05° or more. Bouchardat reports a case with a specific gravity of 1.074, and Pavy one with a specific gravity as low as 1.010, which is certainly exceptional. It should be remembered that the quantity of urea present as well as sugar affects the specific gravity.

The urea is proportionate to the amount of proteid food elements ingested, and as patients are usually fed upon nitrogenous food, urea is naturally increased beyond the normal average. Sometimes two or three times the normal quantity is excreted. Urea, however, always exists in small proportion in comparison with the whole quantity of urine voided. There are some instances in which there is apparently an increased waste of the albuminous tissues of the body, resulting in the production of more urea.

The quantity of sugar present varies greatly; an average may be stated as from thirty-two to thirty-five parts per thousand of urine, but the total may even exceed five hundred grammes per diem.

The effect of a heavy meal of starchy food in increasing the sugar is promptly shown by the urine, usually within two hours, and it lasts during several hours. In some cases very little sugar is eliminated, and yet the symptoms are very severe; in others a great deal is voided and the symptoms are not at all severe, but as a rule applying to a majority of cases, the severity increases or diminishes with the quantity of sugar passed. After grape sugar has disappeared during dietetic treatment, inosite is sometimes found in the urine, as in simple polyuria. Other substances found occasionally in connection with sugar are acetone, alcohol, alkapton, diacetic acid, aceton, -oxybutyric acid, peptones, and fat (lipuria). More or less albuminuria is observed.

While dietetic treatment is in progress the urine should be periodically tested with careful relation to the ingested food, and specimens should be examined which are passed from two to four hours after eating various articles of diet in order to observe as exactly as possible the influence of such diet upon the elimination of glucose.