508 OF SECRETION AND EXCRETION. 



412. Next in importance to urea among the organic products of the meta- 

 morphosis of the azotized constituents of the tissues or of the blood, but 

 ordinarily bearing a very small proportion to it (1 : 45 or 50) in quantity, 

 is Uric Acid (C 10 H 4 N 4 O 6 ). This compound contains 33 per cent, of nitrogen. 

 It probably exists in the urine, partly in the free state, and partly combined 

 or conjugated with the alkaline phosphates. 1 The variations in the daily 

 quantity eliminated are considerable ; and, according to Ranke, whilst in 

 great measure independent of differences in age, sex, height, weight, or tem- 

 perature, stand in close relation with the iugestion of food, diminishing to a 

 minimum of 3.7 grains with abstinence, and rising to a maximum of 32.5 

 grains on a full meat diet. Prof. Haughtou found the average quantity 

 eliminated by those consuming animal food to be 4.55 grains per diem, whilst 

 vegetarians discharged only 1.48 grains. Pollack 2 found that the quantity 

 was relatively large in infants at the breast, varying from 1.5 to 3 grains 

 per diem. It is diminished after the use of Alcohol (Hammond), and after 

 the administration of Q,uiuine (Rauke), and is totally absent when large 

 draughts of water have been taken (Geuth). It is increased after the free 

 use of Tobacco (Hammond), and after the consumption of certain substances 

 introduced into the food, as Glyciu and Urea, but no influence is exerted on 

 its quantity by mental activity or repose (Byasson). The effects of muscular 

 exercise were found by Austin Flint 3 to cause slight increase, the quantity 

 passed by Mr. Westou in his long walk of 317^ miles in five days, being at 

 the I'ate of three grains per diem, whilst during the five days previous to the 

 walk it was 2.26 grains, but the quantity varied considerably on each day, 

 without it being possible to connect this variation with the composition of 

 the food or the amount of the exercise taken. A marked increase has been 

 observed in intermittent fevers, in leukiemia, in peritonitis, phlebitis, and 

 some chronic renal and spinal affections. Uric acid is found in the spleen- 

 pulp in considerable quantities, and also in the lungs, liver, pancreas, and 

 brain ; in the juice of muscles, and in small quantities in the blood (Garrod) 

 in the form of an acid urate of soda or ammonia. 4 It seems, therefore, to 

 be very generally present where active interstitial changes are taking place. 

 The precipitation of Uric acid (usually in combination with potash, soda, and 

 ammonia, and perhaps sometimes with lime), which frequently takes place on 

 the cooling of the urine, must not be regarded as indicative of the presence 

 of an unusual amount of this substance ; since it may depend upon other 

 conditions. It seems to have been clearly proved by Dr. Beuce Jones, that 

 there is no relation whatever between the acidity of the urine, and the abso- 

 lute 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. 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 temperature 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 reduction in its temperature, as by exposure to the 

 cold air of a sleeping-room in the winter. Again, the deposit of uric acid 



1 Byasson, Rev. d. Cours Sciont , 1867-8, p. G10. 2 Loc. cit. 



! New York Mod. Journal, 1871, p. 087. 



4 Thudicliuni, Pathology of tho Urine, p. 97. 



5 See his Contributions to the Chemistry of the Urine, in Philos. Trans., 1849. 



