178 THE SECRETIONS: 



selves, are collected on a filter, dried, and weighed. If the filter 

 with its contents is then incinerated in a platinum crucible, the 

 urate of soda will leave carbonate of soda, which must be con- 

 verted into a sulphate, and determined in that form. From the 

 sulphate of soda we can reckon the urate, and by deducting the 

 latter from the whole amount of alkaline urates, we obtain the 

 amount of urate of ammonia. 



d. Decrease of uric acid. A relative and an absolute decrease 

 of uric acid has frequently been observed. In diabetes mellitus 

 I have sometimes been unable to obtain any trace of it, while 

 in other cases I have found it. If the method described in 

 page 116 fails in yielding any traces of uric acid we are not jus- 

 tified in assuming its entire absence. In doubtful cases we 

 must evaporate a large quantity of urine, and treat the residue 

 with alcohol. The portion of the residue which is insoluble in 

 alcohol must be dissolved in acidulated water, and there is then 

 an insoluble residue left, consisting of mucus, silica, and uric 

 acid (if this constituent be present.) If the nitric-acid test be 

 then carefully applied, we may convince ourselves with certainty 

 whether there is an entire absence of uric acid. 



5. Increase or diminution of the extractive matters and 

 ammonia-compounds. 



An increase or diminution in the quantity of the extractive 

 matters, 1 of the chloride of ammonium, and lactate of ammonia, 



1 [At the meeting of the German Association of Natural Philosophers, held at 

 Nuremberg last September, a paper was read by Scherer, on the extractive matters of 

 the urine. The following are the principal facts he has ascertained. The greater 

 portion of the extractive matters is merely a pigment analogous to those of the blood 

 and bile. It may be thrown down from the urine by acetate of lead, and by treating 

 the precipitate with alcohol and hydrochloric acid, it may be obtained in a state of 

 purity. In healthy individuals it yields from 62 to 63 per cent, of carbon, and from 

 6-2 to 6-4 of hydrogen. In fevers, when there is rapid waste of tissue, and the func- 

 tions of the lungs and liver are inactive, the carbon may amount to 66 or 67, and the 

 hydrogen to 7 '2 per cent. An increase in the quantity of extractive or colouring 

 matter maybe detected by boiling urine in a test-tube, and adding a little hydrochloric 

 acid to it. Urine containing an excess of this colouring matter becomes of a dark 

 colour, and on cooling deposits a brownish, blackish, or frequently an indigo-blue 

 sediment, freely soluble in alcohol. Scherer believes that this colouring matter is 

 formed from the haematin of arterial blood, and that the amount of carbon contained 



