REACTION. 151 



free from its salts in the mucous cells of the stomach. 

 The bases which are freed at the same time remain to in- 

 crease the alkalinity of the blood. Part of them pass into 

 the urine, producing the "alkaline tide," or alkaline reac- 

 tion, which is often noticed at this time. The urine of 

 herbivorous animals is normally alkaline from this cause. 

 On the other hand, an acid food or one from which acids 

 are produced during its decomposition in the body will 

 increase the acidity. Such a one is lean meat, which con- 

 tains acid potassium phosphate, and also sulphur and phos- 

 phorus compounds, which form sulphuric and phosphoric 

 acids by oxidation. Hence the reaction of the urine may 

 be to a considerable extent regulated by the selection of 

 foods. 



Upon standing all urine becomes alkaline by fermenta- 

 tion. This is produced by the action of a number of micro- 

 organisms upon the urea, resulting in the formation of 

 ammonium carbonate: 



CO(NH 2 ) 2 + 2H 2 = (NH 4 ) 2 C0 3 . 



If these ferments are introduced into the bladder by 

 an unclean catheter the same action is often produced 

 there. In chronic inflammation of the urinary tract am- 

 monium carbonate is usually present. The latter alka- 

 linity from ammonium carbonate can be distinguished 

 from that produced by sodium and potassium salts by the 

 litmus-paper's resuming its red color after drying, if am- 

 monia were the alkali, but not otherwise. 



In determining the degree of acidity of the urine by 

 the use of a standard alkaline solution, litmus cannot be 

 used to indicate when the neutralization is complete, on 

 account of the interference of the phosphates. 



