56 THE FEEDING OF ANIMALS 



it clots, which is nothing more than the formation of 

 strings of fibrin, perhaps through the influence of a fer- 

 ment, which has been named thrombin. Fibrin as such is 

 not found in living blood. A remarkable fact is that so 

 long as the blood is retained in the arteries and veins, 

 even if the animal dies and grows cold, this clotting does 

 not appear. 



Serum-globulin is a collective name for several globu- 

 lins, which exist in blood-serum and in the other fluids of 

 the animal body, such as lymph and its allies, including 

 those exudations which pertain to diseased conditions, 

 especially dropsical. 



One more protein has been generally classified as a 

 globulin, although differing in some respects from the 

 other members of this class, and more recently is classed 

 as a phospho-protein. Reference is made to vitellin, 

 which is the principal protein in the yolk of eggs. It is 

 there intimately mixed with certain peculiar phosphorized 

 bodies, which we shall notice later. 



70. Glutenins. These form a large part of nitrogen 

 compounds of the cereal grains and possibly of other 

 seeds. They are insoluble in water, alcohol, and neutral 

 salt solutions, but readily dissolve in very dilute acids 

 and alkalies. The glutenin of wheat, found in the 

 tenacious substance that is left after washing the starch 

 out of wheat flour, is the best-known protein of this 

 class and is an important constituent of wheat flour, 

 existing there on the average to over 40 per cent of the 

 total protein. 



71. Alcohol-soluble proteins.* Alcohol-soluble pro- 

 teins have been found in all the cereal grains so far exam- 



* Osborne and others propose the name prolamins. Science, Vol. 

 XXVI, pages 417-427. 



