Oti Gravelhj and Calculous Concretions. 297 



for some time, having frequently given two scruples of de- 

 siccated soda (containing, according to Mr. Kirwan, 23"94 

 grains,) in the twenty-four hours, for some days together, 

 without any diniinut\on of the usual acidity of this liquor. 



For the information of such of my readers as may not 

 be of the medical profession, I must here observe, that phy- 

 sicians distinguish two kinds of urine: the one rendered 

 immediately after meals, and much dilution, before the 

 process of digestion, or state of sleep, can take place ; al- 

 ways more or less limpid; being comparatively less charged 

 with the natural component parts of urine, (the uree, 

 or extractive colouring matter, in particulai-,) and called 

 ur'ina potus, to distino;uish it from the urina sanguinis, ren- 

 dered many hours afler meals and sleep, the takmg no more 

 than a necessary quantity of liquids, and coniaming the 

 usual proportion of saline and other ingredients ; more espe- 

 cially the uree, to which it owes its natural citrine colour. 



This last, therefore, was that employed in the following 

 experiments, if not otherwise specified ; with the chemical 

 history of which I must suppose gentlemen of the profes- 

 sion now tolerably well acquainted, being so fully and ac- 

 curately detailed in the tenth volume of the Connoissances 

 Ckimiques . 



Having, in the preceding pages, insisted so much on the 

 ncids and acescent drinks as occasional causes of these com- 

 plaints, the first object seemed to be, to ascertain whether 

 the urine of those most subject to them, or actually labour- 

 ing under them, was more relatively acid. We have al- 

 ready seen, from a register of these patients, kept for forty 

 years in the hospital of Luneville, that the early period of 

 life, from two to six years of age inclusive, is jiiost liable 

 to calculous affections. Now, the urine of healthy chil- 

 dren is always found more acid than that of adults, ge- 

 werally in the proportion of two to one. Whilst several 

 drops of the latter are requisite to redden a given quantity 

 of infusion of litmus, a single drop of the former turns it 

 ito a clear red. Paper stained with an infusion of turmeric, 

 and reddened by an alkali, was immediately restored to its 

 colour by a single immersion in the urine of children ; an 

 effect which required some time in that of adults. And 

 that this should be the case we shall not be so irtuch sur- 

 prised at, when we consider the nature of their diet ; and 

 that, in addition to the phosphoric and uric, tluir urine 

 contains the benzoic acid in considerable quantity, the pro- 

 portion of which is found afterwards progressively to di- 

 niinish with their advancement in life. 

 ^ i The 



