606 OF SECRETION AND EXCRETION. 



to be detected by chemical tests. The causes which influence their amount 

 have been carefully studied by Dr. Bence Jones; who has shown that they vary 

 (like urea) with the amount of food ingested, and with the degree of nervo- 

 muscular activity put forth; as might be anticipated from the fact that, under 

 ordinary circumstances, the sulphuric acid is entirely formed within the system, 

 by the oxidation of the sulphur of the protein-compounds, the bases being fur- 

 nished by the alkaline carbonates or phosphates of the blood, whose source has 

 been already considered ( 83). When sulphuric acid or soluble sulphates are 

 taken into the system per se, they partly find their way out of it by the Kidneys 

 ( 88) ; the proportion of sulphuric acid in the urine being for a time augment- 

 ed, although the increase is not considerable until some hours have elapsed after 

 the introduction of these substances into the stomach. 1 The amount of Alka- 

 line Phosphates ( 84) in the Urine is usually about half that of the alkaline 

 sulphates. The acid of these also is ordinarily generated within the system by 

 the oxidation of the phosphorus originally introduced in the protein-compounds; 

 and thus, as in the case of the sulphates, the quantity of them which is excreted. 

 by the urine bears a certain relation to the amount of these compounds ingested 

 as food, and also to the amount of muscular tissue which has undergone disinte- 

 gration by exercise. But it further appears that there is a special relation 

 between the quantity of the alkaline phosphates in the urine, and the amount 

 of disintegration of the nervous tissue ( 361) ; as might have been suspected 

 from the fact that this tissue is distinguished by the very large proportion of 

 phosphorus, united with fatty acids, which it contains ( 345). And a marked 

 increase of these salts is observed in those inflammatory diseases of the brain, 

 in which there is reason to believe that an unusually rapid disintegration of its 

 texture is taking place. 3 The Earthy Phosphates usually bear but a small 

 proportion to the Alkaline ; but their presence in the urine comes to be of great 

 importance, with reference to the precipitates which they form in particular 

 conditions of that secretion. From the researches of Dr. Bence Jones (loc. cit.) 

 it appears that the quantity of these phosphates in the urine chiefly varies with 

 the amount of them contained in the food, into many articles of which they 

 enter largely ( 76, 78); but he has also ascertained that their formation 

 within the system is determined by the presence of their bases ; for, if any 

 earthy salt, a little chloride of calcium or sulphate of magnesia for instance, be 

 taken into the system, the quantity of earthy phosphates in the urine undergoes 

 an increase. The small quantity of carbonate of lime taken into the system 

 with the food ( 77), or set free by the slow disintegration of the osseous tissue, 

 is probably excreted in Man almost entirely in the form of phosphate ; although 

 of the much larger amount ingested by herbivorous animals, a considerable pro- 

 portion is excreted in the urine in its original state. The Earthy Phosphates, 

 although insoluble in water, are soluble in all acid liquids; and they are held in 

 solution in Urine, like the urates, by the acid phosphate of soda. Their preci- 

 pitation in an' alkaline state of the urine is owing to the want of this solvent, 

 not to an excess in their production ; for, as Dr. Bence Jones has pointed out, 

 that excess of alkaline and earthy phosphates in the urine which constitutes the 

 true "phosphatic diathesis," is generally coincident with a highly acid state of 

 the urine. The only other inorganic saline constituent of the Urine whose 



1 Dr. Bence Jones in "Philosophical Transactions," 1849. 



2 See Dr. Bence Jones's valuable series of papers in the "Philosophical Transactions" 

 for 1845, 1847, and 1850, and in the " Medico-Chirurgical Transactions" for 1847 arid 

 1850. It is curious to observe that, whilst the increase in the alkaline phosphates in In- 

 flammatory affections of the nervous centres is very marked, there appears to be a posi- 

 tive diminution of them in Delirium Tremens. A certain allowance must be made, how- 

 ever, for the abstinence from food, which will of itself occasion a reduction in the quantity 

 excreted. 



