2S Experiments on the Urine [Jan, 



even in its most concocted state (viz. when voided on first rising^ 

 in the morning), and when an average has been taken of that of 

 several different persons, to have a higher specific gravity than 

 1020. In the course of the day, also, it falls greatly below that 

 Tiumber ; while the specific gravity of diabetic urine, though 

 subject to a little variation, never changes during the same day 

 to any thing near the same amount. It may be objected, 

 perhaps, to the employment of this test, that it requires more 

 familiarity with the method of taking specific gravities, than falls 

 lo the lot of the greater part of medical practitioners. By 

 means, however, of an hydrometer, which is well known to 

 practical chemists, and which may readily be procured at a small 

 expense, the specific gravity of the urine may be taken in a few 

 moments, and with the greatest accuracy, by a person wholly 

 unaccustomed to experiments of this kind.* 



Respecting the proportion of solid contents, obtainable from 

 diabetic urine, little agreement, as might be expected, is to be 

 found among authors ; for besides that the amount actually 

 varies, it must necessarily depend greatly on the degree to which 

 the evaporation is carried. In Captain Meredith's case, described 

 by Mr. Cruickshank,t it appears, at the maximum, to have 

 constituted rather more than -^-^ of the urine; Dr. Bostock, in a 

 case which he has related in the Memoirs of the Medical Society 

 of London, J obtained ^ of a thick syrup ; Nicholas and Gueude- 

 ville -^V of a mass resembling coarse sugar ; § ; and Thenard from 

 TT Wo' II -^y ^^^^^ process, it will always be found difficult to 

 obtain an exact comparison between the urine of dilFerent per- 

 sons, or of the same patient at different stages of the disease. 

 It appeared to me, therefore, desirable to connect, by a set of 

 careful experiments, the quantity of extractive matter with the 

 more certain character of specific gravity. From such a series 

 of experiments, I have constructed the following table, which 

 -exhibits, at one view, the quantity of solid matter in diabetic 

 urine of different specific gravities between 1050 and 1020. It' 

 will be easy, however, to extend the scale, by the rule of pro^:' 

 portion, to any case in which the urine may be found to have a 

 specific gravity above the former, or below the latter, of those 

 two numbers. In the experiments, which furnished the data of 

 the table, the urine was evaporated by a steam heat, till it 



» The hydrometer best adapted to this purpose is made by Mr. W. Twaddle, 

 of Glasgow. To avoid the inconvenient length of the stem, it is divided into 

 four parts; but it is No. 1 only of the series that is required for determining^ 

 ilie specific gravity of urine. To reduce the d giees of this instrument to the 

 common standard, the rale is, to multiply by ^nd then to add 1000. Thus 6® 

 «f the hydrometer denote a specific stravity of 1030; for 6 X 5 -f 1000 — 1030. 



i In RoUo on Diabetes, 2d edit.'p. 19, X Vol. vi. p. 240. 



^ Aon, de Chim, xliv. 59, [j Ann. de Chim. lix. 47. 



