608 OP SECRETION AND EXCRETION. 



quantity of acid separated from it, and poured into the stomach for the purpose 

 of dissolving the food. The introduction of dilute sulphuric acid into the 

 stomach, even in large doses, was not found to produce any decided change in 

 the acidity of the urine ; the only perceptible effect being a slight diminution 

 of the decrease which takes place after taking food, and a slight augmentation 

 of the increase after fasting. On the other hand, the use of liquor potassae in 

 large doses lessens the acidity of the urine, preventing it from rising after fast- 

 ing to the height it would otherwise attain, and increasing its alkalescence after 

 a meal ; but it does not render the urine by any means constantly alkaline, nor 

 does it hinder the variations produced by the state of the stomach from being 

 very evident. Tartaric acid, in large doses, increases the acidity of the urine, 

 causing it to rise considerably higher than usual after a fast, but not preventing 

 that which is passed a few hours after food from becoming alkaline. Tartrate 

 of potash in large doses, on the other hand, has a marked effect in rendering 

 the urine alkalescent ; still, it does not prevent the usual recurrence of the 

 acidity some hours after a meal. 1 



643. It seems to have been clearly proved by Dr. Bence Jones (loc. cit.), 

 that there is no relation whatever between the acidity of the urine and the 

 absolute amount of Uric acid which it may contain ; for in the urine which is 

 most acid, and which deposits the largest uric-acid sediment, very little uric 

 acid may really exist ; whilst that which contains most uric acid may hold it in 

 perfect solution, and may have but a feeble acid reaction. 3 The main cause of 

 the deposit of Uric-acid sediments is doubtless the presence of some other acid ; 

 for the addition of any acid to healthy urine passed soon after food is always 

 sufficient to produce it. But the deposit takes place less readily if the temper- 

 ature of the fluid be high, since the solvent power of the acid phosphate of soda 

 is then more strongly exerted ; so, on the other hand, a deposit often takes 

 place in urine which would not otherwise exhibit it, through an unusual reduc- 

 tion in its temperature, as by exposure to the cold air of a sleeping-room in the 

 winter. Again, the deposit of uric-acid sediment is favored by concentration of 

 the liquid, which thus augments the proportion of the urate to the water, and at 

 the same time increases the acid reaction ; and thus urine whose constituents 

 are otherwise normal may throw down a copious deposit of this kind, merely 

 from deficiency of water ; whilst an unusual amount of uric acid may be really 

 present without being deposited the urine, too, possessing its ordinary acidity 

 if the proportion of water be large. Thus the uric sediment may be regarded 

 as dependent upon three concurrent conditions : (1) Decrease of temperature ; 

 .(2) Increased proportion of uric acid compound to the water, positively or rela- 

 tively ; (3) Increased acidity of the urine. Sometimes one condition is most 

 influential, sometimes another ; but they are all usually concerned in some de- 

 gree. 



644, The Urine of Herbivorous animals is almost invariably alkaline; partly 

 because their food contains a large quantity of alkaline and earthy bases, in 

 combination with citric, tartaric, oxalic, and other acids, which are decomposed 

 within the system ( 83); and partly because the amount of sulphuric and 

 phosphoric acids, generated as products of the oxidation of the elements of the 

 tissues or of the surplus food, is not sufficient to neutralize them. Such is the 

 condition which occasions the alkalinity of Human Urine, when a portion of 



1 See Dr. Benee Jopes's "Contributions to the Chemistry of the Urine," in "Philosophical 

 Transactions," 1849. 



2 It will be remembered that these sediments nearly always consist of Uric acid in union 

 with a base ( 56); this base is regarded by Prof. Lehmann as chiefly soda; whilst Dr. 

 Bence Jones, in common with Dr. GoLding Bird, maintains it to be ammonia. The term 

 " uric-acid sediment" is used above to designate this compound, whatever maybe the sub- 

 Stance with which the uric acid is united. 



