LIEBIG REVIEWED. 
417 
of plants and animals, but a clear perception of the different actions 
of aliments, poisons, and remedial agents, and of the causes of 
life, and of the exact nature of death. 
According to Liebig, all the substances which constitute the 
food of animals should be divided into two great classes — the nitro - 
genized and the non-nitrogenized. The former serves for the nutri- 
tion and reproduction of the animal body, while the latter minis- 
ters to quite different purposes, being used in respiration, in the 
production of animal heat, and also in that of fat. Out of the 
fifty -five elementary bodies which compose the material universe, 
there are at least twelve of them that enter, more or less, into the 
composition of plants and animals; these are carbon, oxygen, 
hydrogen, nitrogen, sulphur, phosphorus, iron, potash, soda, lime, 
silicon, and magnesia. These simple bodies, as they are called, 
form a part of all organized structures. Moulded into being by the 
hand of creative Wisdom, and endowed with the mysterious and 
incomprehensible principle of life, they become converted into the 
endless race of animals, immense forests, the deep waters of the 
sea, or the atmosphere that supports and retains the vitality of 
living beings. 
“ All nature swarms with life ; one wondrous mass 
Of animals, or atoms organized, 
Waiting the vital breath when parent heaven 
Shall bid his spirit flow.” 
It must be evident that the increase of mass in an animal body and 
the development and reproduction of its organs — depend upon the 
blood, consequently those substances only which are capable of 
being converted into blood can be regarded as nutritious; so, in 
order to ascertain what parts of our food are nutritious and what 
are not, we must first compare the composition of the blood with 
that of the various articles of food. 
When blood is allowed to coagulate, it separates into a yellowish 
liquid — the serum of the blood — and a gelatinous mass, which 
adheres to a rod or stick in soft elastic fibres, when coagulated 
blood is briskly stirred. This is the fibrine of the blood, and which 
is identical in all its properties with muscular fibre, when the latter 
is purified from all its foreign matters. 
The second principal ingredient of the blood is contained in the 
serum, and gives to the liquid all the properties of the white of 
eggs, with which it is identical. When heated, it coagulates into 
a white elastic mass, and the coagulating substance is called 
albumen. 
Caseine is another nitrogenized compound, and is identical with 
cheese. The blood of the young animal, its muscular fibre, cel- 
VOL. XVII. *’ 3 I 
