THE VOLATILE PART OF PLANTS. 99 



cially if a little potash lye be added, it dissolves in a few 

 days to a clear liquid, which coagulates on heating or by 

 addition of metallic salts, in the same manner as a solu- 

 tion of albumin. In very dilute chlorhydric acid, it swells 

 up, but does not dissolve. 



Exp. 48. — Observe the separation of blood into clot and serum ; co- 

 agulate the albumin of the former by heat, and test it with -warm chlor- 

 hydric acid. Tie up the clot in a piece of muslin, and squeeze and wash 

 in water until coloring matter ceases to run off. Warm it with nitric 

 acid as a test. 



Flesh-fihrin. — ^If a piece of lean beef or other meat be 

 repeatedly squeezed and washed in water, the coloring 

 matters are gradually removed, and a white residue is ob- 

 tained, which resembles blood-fibrin in its external char- 

 acters. It is, in fact, the actual fibers of the animal muscle, 

 and hence its name. It is characterized by dissolving in 

 very dilute chlorhydric acid, (one part acid and 1,000 of 

 water) to a clear liquid, from which it is again separated 

 by careful addition of an alkali, or a solution of common 

 salt. 



'Vegetable-fibrin. — ^When wheat-flour is mixed with a 

 little water to a thick dough, and this is Avashed and 

 kneaded for some time in a vessel of water, the starch and 

 albumin are mostly removed, and a yellowish, tenacious 

 mass remains, which bears the name gluten. When wheat 

 is slowly chewed, the saliva carries off the starch and other 

 matters, and the gluten mixed with bran is left behind — 

 well-known to country lads as " wheat-gum." 



Exp. 49. — Wet a handful of good, fresli, wheat flour slowly with a lit- 

 tle water to a sticky dough, and squeeze this under a fine stream ot 

 water until the latter runs off clear. Heat a portion of this gluten with 

 Millon's test. 



Gluten is a mixture of several albuminoids, and contains 

 besides some starch and fat. Vegetable-fibrin is dissolved 

 from it by alcohol, and separates on removing the alcohol 

 by evaporation. 



The albuminoids of crude gluten dissolve in very dilute potash-lye, 

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