INTRODUCTION. 55 



Ptyalin or Salivin, is a substance found in saliva, and 

 Kreatin in the fluids of meat. 



Gelatin colla or glue abounds in the cellular tissue, 

 bones, cartilages, tendons and ligaments. 



It is obtained by boiling, by which means it is soluble, 

 and on cooling becomes a jelly. 



Its chemical elements, according to Mulder, are in one 

 hundred parts, Nitrogen 18.350, Carbon 50.548, Hydrogen 

 6.477, Oxygen 25.125. 



Chondrin forms the basis of the cartilages; it resem- 

 bles gelatin, and exists in the cartilages of the ear, nose, 

 ribs, &c. 



Its chemical composition is made to consist of Nitrogen 

 14.44, Carbon 49.56, Hydrogen 6.63, Oxygen 28.59, Sulphur 

 0.38. 



Both Chondrin and Gelatin also contain phosphate of 

 lime. 



Hcematin forms the coloring matter of the blood, and is 

 found in the envelopes of the colored globules. It con- 

 tains iron, and is soluble in alkalies. When dry it is dark 

 brown, and without taste or smell. 



Pyin, as its name implies, is found in pus, and resembles 

 gelatin. 



Bile. The essential principle of bile, according to Berze- 

 lius, is bilin, which, when dry and in a pure state, is with- 

 out color, transparent, very soluble in water, bitter in 

 taste, not crystallizable, and decomposable by acids. It 

 forms, with acids and bases, soluble compounds, and shows 

 neither acid nor alkaline reaction. 



It is regarded as resinous, and contains a biliary sugar. 



Urea is found chiefly in the urine. It is also discovered 

 in the blood and its secretions, when there is disease of the 

 kidneys. It is obtained by adding nitric acid to the urine 

 after its evaporation to the consistence of sirup, when 

 there is produced the nitrate of urea. The nitric acid is re- 

 moved by the carbonate of barytes, and the urea dissolved 

 in alcohol, which latter is driven off by evaporation. 



