252 PROFESSOR LIBBIG ON THE AZOTIZED 
possible to find the slightest difference between the two bodies, 
either in composition or in their behaviour with reagents. 
It is very remarkable that the identity of the two substances 
has hitherto escaped the attention of chemists, as Braconnot 
says in his treatise on the casein in the milk of animals (Ann. de 
Chimie et de Physique, xliit. p. 347): “I must confess, that in 
examining the seeds of the leguminous plants, before I was ac- 
quainted with the properties of casein, I fell into the error of 
describing legumin as a new and peculiar substance; at present 
it appears to me very much to resemble caseum.” 
Vegetable fibrin is an ingredient of the cereals, especially of 
wheat. It is found in combination with gluten when the dough 
of wheaten flour is kneaded, water being allowed to drop con- 
tinually upon it. Vegetable albumen and starch are carried 
away by the water, and when this has taken place, or when the 
water ceases to be milky, a substance remains of a grayish white 
colour, tough, ductile, and perfectly insoluble in hot or cold 
water. The only difference between vegetable fibrin and albu- 
men is this solubility in water. In this and in every other pro- 
perty it resembles animal fibrin obtained from arterial blood. 
Vegetable albumen is obtained when the viscid part of wheaten 
flour is repeatedly washed with alcohol, till nothing more can 
be extracted; in this process the gluten is dissolved. When 
washed with alcohol, the first matter loses its viscid nature en- 
tirely. It is grayish white, soft and elastic, but not ductile as 
before, and is not free from starch and husks. When flour is 
mixed with water, dilute sulphuric acid added, and the whole 
kept warm until it is as liquid as water, the vegetable fibrin re- 
mains suspended in the liquid, in the form of a gray flocculent 
substance, which must be collected on a filter and washed with 
a weak solution of caustic potash. When carefully neutralized, 
a precipitate of vegetable fibrin and gluten is obtained, which 
alcohol will separate. Vegetable albumen is also contained in 
solution in the juices of plants, and may be extracted by cold 
water from corn and oily seeds. It is distinguished from vege- 
table casein by coagulating when heated, and by not being pre- 
cipitated by acetic acid. When the solution of albumen is very 
dilute, the coagulum does not fall until the solution is evaporated. 
The oily seeds contain vegetable casein and albumen in different 
proportions. When the concentrated milk of the seeds is mixed 
with «ther free from alcohol and allowed to stand, two layers 
