COMPOSITION OF THE URINE. 415 



. ie manner now described, are soluble enough to be always passed off in 

 a fluid form ; but this is not uniformly the case with the Phosphates, 

 which are frequently deposited as sediments of a dead-white aspect, 

 sometimes crystalline, and sometimes wholly or partly amorphous. The 

 crystalline, sediment consists of the triple phosphate, or phosphate of 

 ammonia and magnesia ; the amorphous contains an admixture of the 

 phosphate of lime. The urine, when these are deposited, 1 is usually 

 alkaline, sometimes very decidedly so ; and there is reason to think that, 

 in many cases, this alkaline character, and the deposit of phosphatic 

 sediments, are due to an alkaline secretion from the walls of the bladder 

 and urinary passages, which results from an irritable state of their mem- 

 brane, the urine, as secreted by the kidney, having its usual properties. 

 That an alkaline condition of the urine, resulting from the presence of 

 an unusual amount of bases, is capable of producing a phosphatic deposit, 

 is shown by the simple experiment of adding ammonia to healthy urine, 

 which will occasion a precipitation of the triple phosphate. 



739. But there can be little doubt, that a frequent cause of the de- 

 posit is excessive production of phosphate salts, arising from the in- 

 creased waste or disintegration of Nervous matter, which takes place 

 when it is in a state of unusual activity, either from intense thought, 

 from prolonged exertion, or from continued anxiety. The general prin- 

 ciples already set forth, in regard to the dependence of the functional 

 activity of the Nervous Centres upon a supply of arterialized blood 

 ( 384), show the probability that every act of theirs involves the oxy- 

 genation of a certain quantity of nervous matter. In this oxygenation, 

 phosphoric acid will be produced, from the large amount of phosphorus 

 contained in the nervous matter ; and this will unite in part with am- 

 monia, which is perhaps set free by the same metamorphosis, or is de- 

 rived from other sources ; and in part with bases derived from the food. 

 The experience of every studious man must have shown him (if he make 

 any observations on the matter at all) the frequent coincidence between 

 the presence of phosphatic deposits in his urine, and an excess of men- 

 tal labour ; and there are many instances on record, in which the peri- 

 odical recurrence of the latter has been so invariably followed by the 

 recurrence of the former, that no reasonable doubt can exist as to their 

 mutual connexion. 



740. It is very important for the successful treatment of those Uri- 

 nary deposits, which consist of the normal elements of the Urine, 

 namely, Lithic Acid, and the Phosphates, that the leading facts al- 

 ready stated should be borne continually in mind. In the first place, 

 these sediments may depend upon the general condition of the fluid, 

 and not upon any excess in the constituents of which they are com- 

 posed ; thus a lithic deposit may result from the presence of an excess 

 of some other acid in the urine ; and a phosphatic sediment may be 

 produced by the excess of bases. In such cases, then, our treatment 

 should be directed, not to diminish the quantity of the peculiar consti- 

 tuents of the deposits, but to rectify the state of the Urine on which 

 their precipitation depends. But, in the second place, the sediments 

 may be present in such great amount, as to indicate that their consti- 

 tuents are present in the urine to an excessive degree ; and our treat- 



