246 PROFESSOR LIEBIG ON THE AZOTIZED 
tute of nitrogen, it is necessary to know the composition of 
those vegetable compounds which contain that element. 
If it is found, on inquiry, that the composition of vegetable 
albumen, gluten, fibrin, and legumin, differs from that of the 
blood of animals, or from that of the albumen and fibrin which 
they contain, it is clear that the starch, sugar, and gum must 
give up some portion of their elements to compensate for the 
difference. 
If it is found, for example, that vegetable albumen contains 
the same quantity of nitrogen as animal albumen, but a smaller 
proportion of carbon, or that vegetable fibrin contains less carbon 
than animal fibrin, the necessity would be clearly seen, of adding 
to these azotized vegetable substances the elements of such bo- 
dies as sugar, amylin, and gum, so as to compose animal albu- 
men and fibrin; or, in other words, to form blood. If vegetable 
albumen and fibrin were deficient in carbon, this want would be 
found to be supplied by the sugar, gum, and starch ; for it is re- 
markable that these latter bodies contain only carbon and the 
elements of water, and they would add nothing to the azotized 
compounds but that carbon in which they are supposed deficient. 
But if, on the other hand, it is proved that the azotized nutritive 
principles of plants have the same composition as blood, or as 
albumen and fibrin, then, in whatever way the assimilation of the 
nutriment is conducted, it is clear that the carbon of starch and 
the other compounds destitute of nitrogen cannot possibly be 
consumed in the formation of blood. If vegetable albumen and 
fibrin possess the same proportion of carbon and nitrogen as the 
animal principles of the same name, the latter have no need of 
the carbon of the sugar or starch; as we cannot suppose that 
the one substance should give up a part of its carbon to receive 
an equal quantity of the same element from another substance ; 
such an idea would refute itself. Thirdly, if azotized vegetable 
principles contain a greater proportion of carbon than the com- 
ponent parts of animals, to an equal proportion of nitrogen, 
then every probability at once ceases that sugar, gum, or starch 
should be used in the formation of the azotized animal com- 
pounds, or in supplying the place of what is consumed, because 
the azotized vegetable principles must lose their excess of carbon 
to become either blood or muscular fibre. 
No organ employed in performing any vital function in ani- 
mals, nor any essential constituent of such an organ, is destitute 
