THE KIDNEYS SECRETION OF URINE. 515 



solvent, not to an excess in their production ; for, as Dr. Bence Jones lias 

 pointed out, that excess of alkaline and earthy phosphates in the urine which 

 constitutes the true "phosphatic diathesis," is generally coincident with :i 

 highly acid state of the urine. In Mr. Westou's case before alluded to the 

 average excretion of the phosphoric acid was 50.14 grains per diem for the 

 five days before the walk, for the five days of the walk 76.63 grains, and for 

 the five days after the walk 56.89 grains. The excretion of phosphoric acid 

 is not increased by exercise on a non-nitrogenous diet (Parkes). The abso- 

 lute amount excreted per diem on a mixed diet varies from 54 to 78 grains 

 (Geuth). The only other inorganic saline constituent of the Urine, whose 

 quantity gives it importance, is Chloride of Sodium. By far the larger 

 proportion of this is doubtless derived directly from the food ; but little being 

 furnished by the disintegration of muscle, which will set free potash rather 

 than soda. The amount eliminated by the urine is consequently subject to 

 great variation, it being the function of the Kidneys to remove whatever is 

 superfluous, so as to prevent the blood from becoming overcharged with this 

 substance. In Rauke's experiments on his own person, the quantity dis- 

 charged varied from 75 to 523 grains daily ; ordinarily it varies from 200 to 

 350 grains. Of the chloride of sodium introduced as food, a part appears to 

 undergo decomposition in the system, whereby hydrochloric acid is furnished 

 to the gastric fluid, and soda to the bile ; much of this acid, however, must 

 reunite with its base in the alimentary canal, so that the chloride of sodium 

 thus regenerated will be absorbed with the products of the digestive opera- 

 tion. Its quantity is increased by muscular exertion (Byasson). Dr. Flint 

 found the average amount daily excreted during five days in the person of 

 Mr. Weston to be 159.45 grains for 5 days previous to a walk of 317i miles. 

 During the walk the average was 65.08 grains, and during the five days after 

 the walk 312.40 grains per diem. The quantity is decreased on a non-nitro- 

 genous diet (Parkes). It is much diminished after profuse sweating (Ranke). 

 Although Nitric Acid can scarcely be regarded as a normal constituent of 

 the Urine, yet the investigations of Dr. Bence Jones 1 appear to show that it 

 is formed by a combustive process within the body, whenever ammoniacal 

 salts are introduced into the system ; its amount, however, being very small. 

 He has also found that it is generated after the ingestion of small quantities 

 of urea; a fact which affords some confirmation to the doctrine of Frerichs, 

 that urea may undergo decomposition into carbonate of ammonia, whilst still 

 circulating in the current of blood. The presence of Oxalic Acid in the urine 

 (in combination with Lime) has been usually regarded as a pathological 

 phenomenon, consequent upon an irregular performance of the retrograde 

 metamorphosis of the tissues ; but there can be no doubt that it may also 

 result from the presence of soluble salts of oxalic acid in certain articles of 

 vegetable food. 2 The Gases found in the Urine have been examined by 

 Planer 3 and Bernard. 4 Planer found in one instance 7, and in another 16 

 per cent, of gas. The following Table gives the percentage composition of 

 the gases obtained : 



1 Philosophical Transactions, 1851. It is right to state, however, that this doctrine 

 has been called in question by some eminent authorities, who deny the validity of the 

 test for nitric acid employed by Dr. Bence Jones. 



2 See Dr. Golding Bird on Urinary Deposits. 



3 v. Gorup-Besanez, Physiolog. Cheni., 1862, p. 526. 



4 Le9ons, vol. i, 1859, p'. 347. 



