Composition and Nutritive Value of Strait: 
387 
I'orming matters — a term sometimes applied to the whole group 
of the non-nitrogenized substances. Such mistakes are often 
disseminated by non-scientific men, who meddle with subjects 
on which they are but imperfectly informed ; in which case their 
theoretical deductions, resting on no sound basis, naturally do 
not tally with the observations of practical men. Due account 
being taken of the mischief which palpable errors in science 
produce in the popular mind, it becomes as much the duty of 
the scientific chemist to expose errors as to enrich our treasuiy 
of chemical knowledge by fresh discoveries. 
Little need be said respecting the gum and mucilage in straw. 
Their proportion, though not large, is appreciable, especially in 
somewhat under-ripe samples, in which much more sugar is 
likewise found than in over-ripe samples. Indeed, in the latter 
the amount of sugar is scarcely appreciable. 
Cellular or woody fibre constitutes the bulk of straw, being, of 
course, less valuable than any of the preceding constituents. 
The various non-nitrogenized substances which enter into the 
composition of straw contain, without exception, a large propor- 
tion of carbon, for which reason they are sometimes called car- 
bonaceous matter. Their use in the animal economy is of a 
twofold character — either to supply the materials for the forma- 
tion of animal fat, or to support respiration and consequently 
animal heat. These different carbonaceous substances are not, 
however, equally well adapted to either of these uses, and may 
be divided, according to the fitness and readiness with which 
they fulfil the one or the other function, into- — - 
1. Fat-producing substances. 
2. Heat-producing or respiratory substances. 
3. Indigestible substances. 
To the first belong the oil, fat, and waxy matter, which in 
straw, as already mentioned, seldom amount to much more than 
1 per cent. Oily and fatty vegetable substaiices are eminently 
well adapted to the laying on of fat in animals, inasmuch as the 
composition of vegetable fat is analogous if not identical with 
the several kinds of fat found in the bodies of animals. The 
fatty matters of food, without undergoing much change, are 
therefore readily assimilated by the animal organism, and applied 
when given in excess to the storing up of animal fat. On the 
other hand, substances rich in starch are specially fitted to sup- 
port respiration. Oily and fatty matters, however, when given 
with a scanty supply of starchy food, become available for the 
support of respiration ; and again, gum, starch, and sugar, 
when given to fattening beasts in excess, are transformed into 
animal fat. There is thus no essential difference between the 
fatty or starchy constituents of food in so far as their uses are 
