INGREDIENTS OF THE URINE. 383 



The Alkaline Phosphates, or ordinary phosphates of sodium and 

 potassium. These are the soluble phosphates, which exist in the blood 

 as well as in the urine, and which, in solution, have a mild alkaline re- 

 action. Owing to their ready solubility, they never appear as a precipi- 

 tate, nor disturb in any way the transparency of the urine. It is under 

 the form of these salts that most of the phosphoric acid in combination 

 is discharged with the urine. According to Yogel, the excretion of 

 phosphoric acid by this channel is increased by the use of food contain- 

 ing soluble phosphates or substances capable of yielding phosphoric 

 acid by the changes which they undergo in the system. It is accord- 

 ingly more abundant under a diet of animal food, less so under a vege- 

 table regimen. Its discharge, however, does not depend exclusively 

 upon the ingredients of the daily food, since it continues, although in 

 diminished quantity, after long-continued abstinence from all food. Its 

 immediate origin is, therefore, wholly or partly from the constituents 

 of the body itself. The observations of Wood, 1 as well as those of 

 Yogel and others, show also that there is a diurnal variation of con- 

 siderable regularity in the normal excretion of the salts of phosphoric 

 acid. Its hourly quantity is at a minimum during the forenoon, in- 

 creases in the latter part of the day after the principal meal, and reaches 

 a maximum in the evening or during the night, to diminish again on the 

 morning of the following day. It is under the form of phosphates that 

 the phosphorus contained in certain organic substances (lecithine) is 

 finally discharged from the system. The average quantity of the alka- 

 line phosphates discharged during health under an ordinary diet is a little 

 over four grammes per day. 



The Earthy Phosphates, or the phosphates of lime and magnesium. 

 The earthy phosphates are usually present in the urine in much smaller 

 quantity than the preceding. They are held in solution only by the acid 

 reaction of the urine, and when this is absent or very much diminished 

 they are thrown down as a light precipitate, consequently, the neutral 

 or faintly alkaline urine passed in the forenoon is often slightly turbid 

 with a deposit of the earthy phosphates, without, however, indicating 

 any abnormal increase in their amount. According to the extensive 

 and careful observations of Wood, the alkaline and earthy phosphates 

 differ from each other in the conditions which influence their excretion. 

 "While the alkaline phosphates of the urine are increased in amount 

 during continued mental application, the earthy phosphates are dimin- 

 ished, and the total quantity of both kinds is not materially altered. 

 The earthy phosphates, on the other hand, are increased by abstinence 

 from mental labor. Their average daily quantity under ordinary condi- 

 tions is about one gramme, or rather less than one-quarter that of the 

 earthy phosphates. 



1 On the Influence of Mental Activity on the Excretion of Phosphoric Acid by 

 the Kidneys. Proceedings of the Connecticut Medical Society, 1869. 



