URINARY DEPOSITS. 783 



of the tissues ; but even these are, of course, ultimately derived from 

 the food. The sulphates and phosphates of the alkalies, originate in 

 the oxidation of the sulphur and phosphorus belonging to the albumi- 

 noid substances found especially in the muscular and nervous tissues ; 

 the quantity of these salts is increased by exercise, which conduces to 

 changes in those tissues. The earthy phosphates must also be ulti- 

 mately derived from the food, either directly, or through tissue 

 changes ; their quantity appears to increase, on the administration of 

 chloride of sodium. The chloride of sodium itself varies in quantity, 

 according to the amount consumed with the food ; one office of the 

 kidneys is to regulate the quantity of that salt retained in the blood. 

 The ammonia of healthy urine occurs chiefly in the triple phosphate of 

 ammonia and magnesia ; it is an ultimate product of the decomposition 

 of albuminoid substances, the creatin, creatinin and urea being prob- 

 ably intermediate stages. 



Under certain circumstances, amorphous or crystallized deposits, or 

 sediments, are formed in the urine ; and sometimes, even solid concre- 

 tions, named urinary calculi or stones, occur in it even within the body. 



The most common sediment is of a yellowish or reddish hue, and 

 consists of mixed urates and uric acid, with some of the coloring prin- 

 ciples ; these being less soluble in cold than in hot fluids, may be pre- 

 cipitated from urine, clear at the time of its discharge from the body. 

 When turbidity exists at the moment of discharge, or subsequently, 

 though the urine be maintained at the temperature of the interior of 

 the body, the condition must be regarded as one deviating from health. 

 But a uric acid sediment may be caused by an acid fermentation of 

 the urine, often associated with the growth of penicillium. The acid 

 then formed, usually lactic acid, decomposes the urates in solution, and 

 uniting with their base, whether soda or ammonia, precipitates the less 

 soluble uric acid. The colored extractive matters may, through changes 

 produced in them by atmospheric action, increase the solvent power 

 of the fluid for the urates, and so prevent their precipitation in the pro- 

 cess of cooling. The quantity of uric acid sediment, therefore, does 

 not necessarily correspond with that in the urine itself, for sometimes 

 it may be precipitated, though existing in small proportion, and some- 

 times be suspended, though present in larger quantity. If the uric 

 acid compounds be in excess, the temperature lowered, and a free acid 

 be formed, a deposit is sure to take place. In hot climates, the cuta- 

 neous excretion is very active, a quantity of acid is thus removed from 

 the system, and deposits of lithic acid are accordingly rare. Phos- 

 phatic sediments are also occasionally met with, owing to peculiar de- 

 compositions or fermentations, affecting the urea, which is then con- 

 verted into carbonate of ammonia ; by this, the earthy phosphates are 

 precipitated, as ammoniacal magnesian phosphate, or as phosphate of 

 lime. This alkaline fermentation occurs sooner or later, at certain 

 temperatures ; but in those diseases in which the urine is too long re- 

 tained in that viscus, and also in inflammation of the urinary mucous 

 membrane, it sometimes happens in the bladder itself. This form of 

 alkalinity is to be distinguished from that which depends on the pres- 

 ence of potash or soda ; in the latter case, the blue color given to lit- 



