§ 114. SOLID EXCREMENTS. 223 



h. Sulphuric acid. — Heat 50-100 c.c. of the urine, add 

 some nitric acid, and then baric chloride in slight excess 

 (§ 59). 



I. Sulphur. — To determine total sulphur, mix 50 c.c. of 

 the urine in a silver crucible with solid caustic potash and 

 a little saltpetre; evaporate the mixture cautiously to 

 dryness, ignite the residue strongly until it is quite white, 

 exhaust it with water, and determine sulphuric acid in the 

 filtered solution, in the usual manner. 



m. Carbon and Hydrogen. — Absorb 10 c.c. of the urine 

 by fine quartz sand that has been previously boiled with 

 acid, washed, and ignited, dry the mixture, and bnrn it 

 with plumbic chromate. (See Fresenius's Quantitative 

 Analysis.) 



SOLID EXCREMENTS. 



114. The solid excrements of the herbivora are exam- 

 ined by almost precisely the same methods as are given 

 for the analysis of fodder (§ 129). 



In the determination of woody fibre, owing to the pres- 

 ence of resinous matters it is often necessary to boil the 

 substance with alcohol before treating it with dilute acid 

 and alkali. 



Microscopic examinations arc often useful in the exami- 

 nation of these excrements, in order to ascertain what 

 parts of the plants, that were consumed as fodder, remain 

 undigested. For this purpose, it is well to knead a por- 

 tion of the substance in a linen bag under cold water un- 

 til the latter is no longer made turbid. Starch, crystals 

 of diflicultly soluble salts, and grains of sand, may be 

 looked for in the sediment deposited from the water used 

 in washing, after long standing, while sugar, gums, lactic 

 acid, etc., may be sought for in the solution ; the residue 

 in the bag may be examined with the microscope, with or 

 without previous boiling with alcohol to remove resinous 

 matters. 



