190 
liebig's organic chemistry. 
17 per cent, at least, of nitrogen, together with carbon, hy- 
drogen, and oxygen; and in some are found, more especial- 
ly, the inorganic elements contained likewise in blood, iron, 
lime, phosphorus, magnesia, &c. 
Such being the composition of the blood, and its ready 
formation from organized animal structure, this structure 
will then afford the materials most readily assimilated, and, 
in carniverous animals, the function of digestion will be ex- 
hibited in the most simple form. Organized structure, de- 
rived originally from blood, becomes dissolved in the sto- 
mach, and, in the course of its transmission through the 
system, becomes again blood, to be again transformed into 
organized structure. 
But, in gramnivorous animals, this process is not so evi- 
dent. Food, apparently very distinct in its character, is 
here assimilated and undergoes the same changes. Chemical 
research explains with satisfaction this result. Vegetable 
matter is found to contain the same ultimate elements as 
animal organism, and, what is much more remarkable, com- 
bined to form certain proximate ingredients, which not only 
possess similar chemical characters with albumen and fibrine, 
but, by analysis, are proved to be identical in composition. 
These nitrogenized constituents of vegetable food are, vege- 
table albumen, fibrine, and casein. They are identical in 
properties with the chief constituents of blood, and the iden- 
tity among all extends to their ultimate composition, so that 
no difference in their elementary formation can be observed. 
This similarity in composition can even be traced to a still 
greater extent. According to the observations of Mulder, 
all these nitrogenized compounds, whether vegetable or ani- 
mal, yield, under the action of a solution of caustic potassa 
and heat, a solution from which acetic acid precipitates a ge- 
latinous substance, (proteine,) in all cases identical. In ul- 
timate composition, proteine differs from all the tissues by 
containing an additional amount of oxygen and hydrogen, 
to which, also, in some degree, phosphorus, sulphur, and ni- 
