the Urine in Man and Carnivorous Animals. 477 



lysis of urine, when made without respect to the inorganic 

 salts, acids and bases supplied by the aliments, teaches no- 

 thing whatever, and by no means justifies us in drawing there- 

 from any physiological or pathological inference ; secondly, 

 that from the nature of the ashes of the aliments we are able 

 to determine, positively, the constituents of the urine emitted ; 

 and thirdly, that only when these latter have been distinctly 

 ascertained can we expect to derive, from the analysis of the 

 urine, any correct information with respect to the inorganic 

 matters which have come to be present in it through pro- 

 cesses of disease ; this, at least, is the chemical method of quan- 

 titative investigation. 



Bearing in mind that the urine contains the soluble consti- 

 tuents of the ashes of the aliments, whilst the faeces contain 

 the insoluble part of these constituents, we may from an accu- 

 rate knowledge of both, at once determine in which urine so- 

 luble alkaline phosphates must be present, and in which they 

 cannot exist. The ashes of all seeds, and of flesh and blood, 

 contain a certain amount of soluble and insoluble phosphates, 

 whilst the ashes of vegetables contain no free alkaline phos- 

 phate, but only insoluble phosphates. These vegetable ashes 

 contain far more lime and magnesia than is required for the 

 neutralization of the phosphoric acid present. Hence, upon 

 incinerating a plant, together with its seed,, and lixiviating the 

 ashes, we find in the fluid obtained no alkaline phosphate, 

 although the lixivium of the ashes of the seeds, when incine- 

 rated and lixiviated by themselves, yields a considerable 

 amount of these phosphates ; the excess of lime and magnesia 

 contained in the leaves and the straw enter here into combi- 

 nation with the phosphoric acid of the soluble alkaline phos- 

 phates, forming an insoluble compound. 



It will now be understood why the alkaline phosphates are 

 generally absent from the urine of herbivorous animals, and 

 also why, in certain cases, they may be found in the urine of 

 these animals. If the nutriment of these animals contains no 

 soluble phosphates, their urine cannot contain any, whilst if 

 we add a certain proportion of grain to their food, the alka- 

 line phosphates may be detected in their urine. Thus it is 

 obvious, likewise, that the soluble phosphates in the urine of 

 man are merely accidental constituents, and that by simply 

 adding lime or magnesia to the aliments, and thus assimilating 

 the constitution of these aliments to that of the food of herbi- 

 vorous animals, the urine must become altered in its nature 

 and properties. The knowledge of the influence which alka- 

 lies, magnesia and lime, or acids, exercise upon the proper- 

 ties of the urine, or, in other words, upon the secretory pro- 



