386 LIQUID PARTS OF ANIMALS. 



The following are the characters of these four divisions : 



1. The substance already mentioned as existing in saliva in 

 white flocks, and considered as mucus. It amounted in this case 

 to 0-42 per cent, of the saliva. 



Acetic acid causes it to swell up and to become gelatinous. But 

 no solution takes place even at a boiling temperature. Sulphu- 

 ric acid gives it a red colour, but produces no further alteration. 

 Muriatic acid dissolves it, and the colour of the solution is blu- 

 ish. This colour is produced slowly when the acid is cold ; but 

 more rapidly at a boiling temperature. Ammonia behaves like 

 acetic acid. Caustic potash causes a slight swelling, scarcely 

 perceptible, but does not dissolve it. 



2. The substance soluble in water, but insoluble in alcohol 

 of 0*863, and amounting to 0*527 per cent., is what chemists 

 have denominated salivin or ptyalin. Its characters were first 

 described by Berzelius.* It was afterwards examined by Leo- 

 pold Gmelin. The characters given by these two chemists dif- 

 fer in consequence of the different methods employed to obtain 

 the salivin. For heat alters its properties. Its characters have 

 been detailed in the first part of this volume, while treating of 

 animal substances. 



3. The matter soluble in water, but insoluble in alcohol of 

 0*800, consists chiefly of the salts contained in saliva ; but is not 

 quite free from animal matter. It amounts to 0*443 per cent, of 

 the saliva. It has a yellow colour and does not deliquesce. Its 

 solution is not altered by chloride of barium, sulphuric or muria- 

 tic acid, corrosive sublimate, chloride of iron, nor by infusion of 

 nut-galls. Acetate of lead gives a white precipitate, not redis- 

 solved by acetic acid or water. Nitrate of silver throws down a 

 white precipitate soluble in ammonia. When burnt it gives out 

 the smell of animal matter, and leaves a coal containing potash 

 and soda. Probably the animal matter which it contains is salivin. 



4. The matter soluble in water and in alcohol of 0*800, 

 amounted to 0*287 per cent It had a yellowish red colour, and 

 deliquesced rapidly if the alkali had not been neutralized. It 

 gave, when burnt, the same products as the other substances, 

 and left a potash and soda salt 



The properties of this substance are best observed when the 

 saliva has been previously neutralized by sulphuric acid. If we 



* Annals of Philosphy, (1st series,) ii. 380. 



