solution of caustic potash (liquor potassa): the other a solution of sulphate of copper of moderate strength. Both solutions must of course be ascertained to be chemically pure and not contaminated with the salts of lead or other impurities. By means of these reagents (sulphate of copper and liquor potassa), we apply what are now familiarily known as Moore's and Trommer's tests, which may be briefly described.

If

Moore's test consists in putting a portion of the suspected urine in a test tube (one-third full), and adding to it half its bulk of liquor potassæ, and then boiling it over a spirit lamp for a few minutes. sugar is present, the urine, thus treated, assumes a brownish colour, which increases in intensity as the boiling is continued. This change is caused by the formation of glucic acid which becomes transformed into melassic acid. The intensity of colour produced by this test depends on the quantity of sugar present in the urine: if the quantity is minute, the urine will become like pale sherry; but if large, the colour will resemble that of port wine or claret, or in some specimens it will become almost black. Between these two extremes, shades of varying intensity will be observed in different samples of urine.

Trommer's test is applied by adding to a portion of the urine, in a test tube, a drop or two of a solution of sulphate of copper so as to produce a pale blue colour, and then adding liquor potassæ, in excess, until the hydrated oxide of copper, first thrown down, is re-dissolved, as it always is when sugar is present, and a clear deep blue fluid is produced: this latter is next boiled over a spirit lamp, and if the quantity of urine sugar is minute, a yellowishred opalescent tint will be produced; but if the amount of sugar is large, a copious opaque orangecoloured precipitate of the sub-oxide of copper is thrown down. If, however, sugar is altogether absent from the urine, a dark green precipitate is formed by the boiling.

These two tests for diabetic sugar are sufficient for ordinary clinical examinations, although there are others more delicate still. The old and familiar fermentation test has fallen, in a great measure, into disuse, in consequence of the length of time required for its completion, and the readiness with which the others can be applied.

As already stated, increase in quantity and elevation in density are conditions generally co-existent in the urine of diabetics, so that the degree to which they are developed supplies a very reliable practical

guide as to the quantity of sugar voided in any particular case of the disease, and an index by which we can safely predicate whether the amount is small or large. But when it is considered necessary to determine the exact quantity of sugar in any given specimen of urine, we must have recourse to a more definite procedure. For this purpose various methods are employed. One of the simplest and most ingenious of these is the beautiful apparatus invented by Soleil and named the polarising saccharimeter, by which the quantity of sugar is accurately measured by the degree of polarisation produced. This instrument is made by some London philosophical instrument makers; it is much used in France, but is not generally known in this country.

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CHAPTER VI.

PATHOLOGY OF DIABETES. SOURCE OF THE SUGAR.
MAL-ASSIMILATION OF THE PROXIMATE PRINCIPLES

OF FOOD; OF STARCH AND SUGAR; OF FAT; AND
OF ALBUMEN.

ALTHOUGH the urine-sugar in diabetes is immediately derived from the blood, there can be no doubt whatever that the ultimate source is the food. In every case of the disease more or less of the food taken, according to the stage and severity of the affection, is converted into diabetic sugar in the system. The saccharine metamorphosis, or malassimilation, in fact constitutes the disease. But as food is composed of an admixture of carbonaceous and nitrogenous proximate principles, it is necessary to enquire into the influence exercised by each and all of these compounds, or principles, on the quantity of sugar formed and subsequently excreted in the urine, or, in other words, on the activity of the morbid process.

Experience has clearly demonstrated that in

diabetes, as a general rule, all kinds of vegetable food containing amylaceous and saccharine substances increase the quantity of sugar in the urine : the augmentation commencing in less than two hours. after such food has been taken, and generally continuing from four to six hours, and even much longer when the quantity of starch has been large.

A very important fact, throwing considerable light on the pathology of the disease, has been established by careful experiment and observation in several cases, namely: that in the early period of the disease the whole of the sugar found in the urine is derived from the starch and sugar in the food. This seems to be proved by the following observations. Mr. Graham' ascertained that in two cases of diabetes kept carefully under examination for a period of two months, the quantity of diabetic sugar voided never exceeded the amount of starch taken in the food, and that nearly the whole of the starch consumed was accounted for by the sugar in the urine. Traube has also recorded a case in which at first all the diabetic sugar detected in the urine was derived exclusively from the starch in the food. Dr. Parkes,2 too, refers

1 See article on Adventitious Products, by Dr. Walshe: Cyclop. of Anat. and Physiolog.

2 Op. cit. p. 347.