284 NON-NITROGENOUS NEUTRAL BODIES. 



sulphate of silver ; the fluid freed by filtration from the chloride of 

 silver was evaporated., and the sugar was obtained in a state of 

 chemical purity by extraction with alcohol ; in order to remove 

 any traces of this fluid, it must be recrystallised from distilled 

 water. 



Tests. The methods of testing for sugar are not merely of 

 importance in enabling the physician to establish his diagnosis in 

 cases of diabetes mellitus, but likewise in consequence of the 

 physiological relations of sugar to the general metamorphosis of 

 tissue. Many chemists (amongst whom may be enumerated 

 Golding Bird*, Gairdnerf, BudgeJ, and myself,) have turned 

 their attention to the most accurate methods of discovering sugar. 

 There has been much discussion regarding Trommer's|| admirable 

 test for sugar; but if this test be not admitted, equal objections 

 may be advanced against all the reagents employed in mineral che- 

 mistry ; for these also require to be used with proper care and circum- 

 spection ; the application of most of them demanding more precaution 

 and skilful manipulation than this test. It may be regarded as infal- 

 lible for the recognition of the presence of sugar in diabetic urine ; 

 although a person utterly ignorant of chemical reagents may also 

 here fall into error. In true Diabetes mellitus, the urine is free 

 from those substances which may interfere with the reaction on 

 which this test is founded, or rather with the judgment we form 

 regarding this reaction; diabetic urine presents this difference from 

 other saccharine urine, that the former with sulphate of copper 

 and potash gives the reaction almost as readily as a pure solution of 

 grape-sugar would do, even when there is but little sugar present, 

 whilst the more normal urine in which sugar is a mere incidental 

 constituent, gives a less distinct reaction ; and the latter moreover 

 precipitates other substances with the suboxide of copper, by 

 which the colour of the precipitate is considerably modified. 



The question here arises what precautionary measures ought 

 to be observed in the application of Trommer's test ? 



The fluid to be examined is treated with caustic potash, and. 

 filtered if necessary, that is to say, if there be too great a precipi- 

 tate ; an excess of caustic potash is productive of no harm, as it 



* Monthly Journal of Medical Science, vol. 4,,p. 423, [and " Urinary Deposits,*' 

 3rd Ed. p. 352. G. E. D.] 

 t Ibid. p. 564. 



$ Arch. f. physiolog. Heilk. Bd. 3, S. 385. 

 Schmidt's Jahrb. Bd. 45, S. 6-10. 

 || Ann. d. Ch. u. Pharm. Bd. 39, S. 360. 



