492 
DU. PROUT ON ANIMAL CHEMISTRY. 
acid, the zoonic acid, &c., which have been proved to consist 
essentially of acetic acid, mixed with small portions of foreign 
bodies. 
A third, and most important set of bodies belonging to this 
group, is lignin> or the woody fibre. This at present is only 
known to exist in the merorganized form, but its crystallized 
parallel will be probably discovered hereafter. The woody fibre 
is used as an aliment by many of the lower animals, and it may, 
by the united agencies of heat and moisture, be converted into a 
species of the amylaceous principle, highly nutritious. 
Another set of bodies belonging to this class is the gummy or 
mucilaginous , of which gum arabic may be considered as an ex¬ 
ample among merorganized bodies, and sugar of milk among the 
crystallizable. 
If we consider carbon as the measure of the nutritive powers of 
alimentary bodies in general, which may, perhaps, be fairly done, 
it may be stated generally that the capacities of the different 
bodies belonging to the saccharine group, viewed in this light, lie 
between one-third and a half of their weight. 
2. Of the Oleaginous group .—I have analysed many speci¬ 
mens of the more important varieties of this group of bodies, and, 
as formerly stated, have found them all to be essentially composed 
of olefiant gas and water, in different proportions, or having refer¬ 
ence to this composition. These analyses have not yet been pub¬ 
lished. Oily bodies are naturally separated by their sensible and 
chemical properties into two great divisions, viz., fixed and vola¬ 
tile oils. The volatile oils, in general, are not used as aliments; 
and hence we have little to do with them here, unless, indeed, we 
except alcohol, which, though conforming in its composition to 
the fixed oils, more nearly resembles in its properties the volatile 
ones. We owe much of the information we possess respecting the 
chemical properties of fixed oils to M. Chevreul; and in procur¬ 
ing the different principles for analysis, I have generally followed 
his instructions, for which, therefore, I refer to his works. If, as 
before, we consider carbon as the measure of the nutritive powers 
of oily bodies, we shall find that they far surpass the saccharine 
principles in this respect; the carbon of the fixed oleaginous 
bodies varying from seventy to eighty-one per cent., while alcohol, 
containing fifty-one per cent., holds a sort of intermediate place 
between the two classes, or rather commences where the saccharine 
bodies terminate. 
3. Of the Albuminous group .—This group of alimentary sub¬ 
stances differs from the preceding in containing azote, which ren¬ 
ders their analysis so difficult and troublesome, that I cannot yet 
venture to mention publicly the general law that determines their 
