96 PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



the gluten-fibrin separates. It dissolves in warm, dilute alcohol, and 

 forms a brownish-yellow solution. When such solutions cool, and as 

 they undergo evaporation, a white or grayish pellicle forms on the surface, 

 which disappears on agitation. It is more soluble in absolute alcohol 

 than either gliadin or mucedin. Gluten-fibrin is readily dissolved in 

 dilute acid and alkaline solutions, and is precipitated from these solutions 

 by neutralization, or by the addition of metallic salts. 



3. Gliadin, or Vegetable Gelatin. — This body is one of the principles 

 of gluten which is soluble in dilute alcohol. It is obtained by agitating 

 gluten with strong alcohol, which removes gluten-fibrin, dissolving the 

 residue in 1 per cent, potash solution, and, after having precipitated the 

 solution with acetic acid, by extracting the precipitate with alcohol of 

 75 per cent, at a temperature of 38° C. By this means onby gliadin is 

 dissolved, while the mucedin remains. Vegetable gelatin then separates, 

 as the fluid cools, in the form of a gelatinous mass. It may be purified 

 by dissolving in acetic acid and neutralizing the clear solution with 

 potash ; the precipitate is then again washed with alcohol and ether. In 

 the fresh state vegetable gelatin has the consistence of a thick mucilage. 

 Absolute alcohol causes it to contract to a hard and yellowish-white 

 mass. Cold water causes it to again swell up and dissolves part of it, 

 and the solution may be precipitated by tannic acid. Submitted to long- 

 boiling with water, gliadin becomes insoluble and undergoes partial 

 decomposition. Dilute alcohol dissolves it more readily than pure water. 

 It is insoluble in absolute alcohol. It is very soluble in acids and dilute 

 alkalies, and while in solution in alkalies may be precipitated by the 

 metallic salts, but its solution in acetic acid is not precipitated by 

 mercuric chloride. It contains a considerable percentage of sulphur. 



4. Mucedin.— This "substance has been but little studied, and is only 

 to be distinguished from vegetable gelatin by its greater solubility in 

 water. Its method of isolation has been already indicated in the pre- 

 ceding paragraphs. 



These substances approach one another very closely in chemical 

 composition, and it would appear from the processes employed in their 

 isolation that it is by no means certain that they have been obtained 

 pure. On the other hand, their analogy to corresponding bodies of 

 animal origin is not sufficiently striking to justify an analogous nomen- 

 clature. 



For the preceding account of their properties we are indebted 

 mainly to Wiirtz (Chimie Biologique). 



II. Globulins.— Globulins are bodies which are insoluble in water 

 but soluble in dilute solutions of sodium chloride. They are coagulable 

 by heat when in solution, and, while soluble in dilute acids and alkalies, 

 are in the process of solution changed into derived albumens. They are 



