1056 SOLID PARTS OF ANIMALS. 



before the blow pipe into a pearly globule. Part of it dissolves 

 in acetic acid, the rest in hydrochloric acid. 



7 The uric acid calculus is perhaps the most common. It 

 is usually of an oval form, of a brownish or fawn colour and 

 smooth surface, and composed of concentric layers round a 

 central nucleus, which is often foreign matter. Consisting of 

 volatile elements, like the first and second species, it is con- 

 sumed before the blow pipe, leaving only a trace of white ash. 

 The powder of this calculus is soluble in a dilute and warm 

 solution of caustic potash, and on adding an acid, uric acid is 

 precipitated as a white powder. It is dissolved with effervescence 

 by nitric acid of the ordinary strength, and the solution when 

 evaporated nearly to dryness, and treated with a drop of am- 

 monia exhibits the beautiful pink colour of murexide (see uric 

 acid, page 1003). The formula for uric acid is C 10 H 4 N 4 O 6 . 



8. The urate of ammonia forms a comparatively rare calculus. 

 It has the chemical properties of the last species, with the 

 additional property of emitting ammonia when dissolved in a 

 dilute and warm solution of caustic potash. 



SECTION VIII. 



SOLID PARTS OF ANIMALS. 



Bones. When bones are digested in very dilute hydrochloric 

 acid, their earth is dissolved out, and an organic matter remains, 

 consisting of cartilage, which retains the form of the bones. 

 This matter when moist is flexible and elastic ; by drying it 

 shrivels up and becomes brittle, but remains translucent. It is 

 entirely dissolved by boiling in water, and gives a solution of 

 gelatin (page 1036). Water heated above 212, under pressure, 

 dissolves the cartilaginous matter entirely out of bones, and 

 leaves the pure bone-earth. 



When bones are distilled in a close vessel, they yield ammo- 

 nia and oily volatile products, while the earth remains behind, 

 black, from the presence of 8 or 10 per cent of charcoal, which 

 in this divided state and associated with the earth, has a high 

 decolourising power. It forms animal charcoal, bone or ivory 

 black. Bones burn white, on the other hand, in an open fire, 

 and leave the bone-earth. T ne phosphate of lime in bones is 



