92 HOW CROPS GROW. 



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

 nitric acid as a test. 



'Flesh-Fibrin. — If a piece of lean beef or other dead 

 animal muscle be repeatedly squeezed and washed in 

 water, the coloring matters are gradually removed and a 

 white residue is obtained which resembles blood-fibrin in 

 its external characters, and as it represents the fibers of 

 the original muscle, aud was supposed to be a simple 

 albuminoid, it was formerly designated flesh-fibrin. It 

 is, however, a mixture consisting largely of myosin {aee 

 p. 97). It mostly dissolves in very dilute hydrochloric 

 acid to a clear liquid, from which addition of much com- 

 mon salt, or of a little alkali, throws down syntonin. 

 The term flesh-fibrin is therefore no longer properly em- 

 ployed to designate a distinct chemical substance. 



Vegetable fibrin. — When wheat-flour or rye-flour is 

 mixed with a little water to a thick dough, and this is 

 washed and kneaded for some time in water, the starch 

 and albumin are mostly removed, and a yellowish tena- 

 cious mass remains, which bears the naxae 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, fresh, wheat-flour slowly with a lit- 

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

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

 Millon's reagent. 



Gluten is a mixture of several albuminoids, and con- 

 tains also some starch and fat. When boiled with alco- 

 hol it is partially dissolved.* The portion insoluble in 



* The dissolved portion Eitthausen found to consist of two distinct 

 alhuminoid or rather glutiiioid bodies, viz. : 



Olicuim, or vegetable glue, is very soluble in water and alcohol. It 

 strongly resembles animal glue and chiefly gives to wheat dough its 

 tenacious qualities. 



Mveedin resembles glladin, but is less soluble in strong alcohol, and 

 Is insoluble in water. When moist, it is yellowish-white in color, has 

 a silky luster, and slimy consistence. If exists also in gluten made 

 from rye grain. (Eitthausen, Jour, filr Prakt. Chem., 88, 141, and 99, 463.) 



