436 ALBUMINOUS COMPOUNDS. 



2. Alkali albunrinates (Protein*) do not yield potassium sul- 

 phide with liquor potassae. 



28. V. Acid Albumins, or Syntonin. Insoluble in 

 water or in XaCl solution. Easily soluble in dilute hydro- 

 chloric acid. Precipitated from solution by neutralization, 

 even in presence of alkaline phosphates. 



29. VI. Amyloid. Insoluble in water, dilute hydrochloric 

 acid and sodium carbonate ; in solutions of NaCl it does not 

 perceptibly swell. It is colored reddish-brown or violet by 

 iodine. It is not digested by gastric juice at the temperature 

 of the blood. 



30. VII. Coagulated Albuminous Bodies. Insoluble in 

 water, very dilute hydrochloric acid and sodium carbonate; in 

 NaCl solutions they do not swell up perceptibly. They are 

 colored yellow by iodine. They are readily converted into 

 peptones by gastric juice at the temperature of the blood. 



31. VIII. Peptones. Soluble in water, not precipitated 

 from the solution by acids, alkalis, or heat. 



33. Decomposition of Albumin. The decomposition of 

 albumin by various agencies is of great interest, as it is only 

 bv a study of the way in which it splits up that a knowledge 

 of its constitution can be obtained. 



When treated with powerful oxidizing agents albuminous 

 bodies yield formic, acetic, propionic, butyric, valerianic, ca- 

 proic, and benzoic acids and the corresponding aldehydes, am- 

 monia, and volatile organic bases. 



Such substances are, however, too far removed from albumin; 

 it is not from these final products of its decomposition that 

 much information is to be got, but rather from those bodies of 

 a tolerably complex nature into which it first splits up when 

 treated with less active decomposing agents. These may after- 

 wards undergo further decomposition, and yield substances of 

 a simple constitution. 



The most important decomposition is that which albuminous 

 bodies undergo when boiled with water or with acids, or when 

 subjected to the action of one of the pancreatic ferments. Under 

 such circumstances peptones are first formed, and afterwards 

 split up, yielding leucinc and tyrosine. 



34. Peptones. These are distinguished from other albu- 

 minous bodies by not being precipitated by boiling, by alkalis 

 or acids, nor by acetic acid and potassium ferrocyanide. They 

 art precipitated by alcohol. Unlike albumin, they diffuse easi!}' 

 through vegetable parchment. With caustic potash and a 



of cupric sulphate, they give a precipitate, which dissolves 

 on shaking, and forms a solution of a red color, becoming violet 

 on the addition of more copper sulphate. 



1'xxlirs which closely resemble the peptones formed during 

 digestion may be prepared by boiling albuminous bodies, such 



