140 ANIMAL SUBSTANCES. 



stones formed in the bladder called calculi, are 

 almost entirely composed of nric acid. This acid, 

 however, exists in urine even in its most healthy 

 state. 



The amniotic acid is found in the liquor of the 

 amnios of a cow. It separates in white crystals. 



The saccho-lactic acid is formed by acting on su- 

 gar of milk, or on gum by the nitric acid. It 

 forms salts called saccho-lactates. 



The sehacic acid is procured from animal fat. It 

 becomes solid, is of a white colour, with a taste 

 slightly acid. 



The Prussic acid has been described, p. under 

 the name of the hydrocyanic acid. 



The formic acid is an acid procured from ants. 



Animal resins. — Peculiar tesins have been found 

 in certain animal substances, as in the bile, amber- 

 gris, &c. 



Animal sugar is found in milk, also in the urine 

 in certain diseases. It is similar to common sugar. 

 " Blood, when suffered to rest, separates into two 

 parts J the one a coagulum or clot, called the 

 crassamentum ; the other, a fluid called the serum. 

 The crassamentum consists of fibrin mixed with al- 

 bumen and colouring matter. The colouring part 

 of blood consists of extremely minute globules of 

 a red colour, which float in the serum, and may be 

 seen by the microscope. The red colour of blood has 

 been supposed to be owing to iron which was oxy- 

 dated by the air in the lungs, but this theory is 

 now rendered questionable. The serum is com- 

 posed of albumen, and also contains a small por- 

 tion of alkali and other substances. It is coagu- 

 lated by heat, the acids, and alkohol. 



Bone is composed of gelatine, another substance 

 which seems t5 be analogous to cartilage or coa- 



