FOODS, IN RELATION TO RESPIRATION AND FEEDING. 353 
for its support must be in a direct ratio with the quantity of oxygen taken 
into its system.” 
And again at page 322 :— 
“ But the waste of matter, or the force exerted, always stands in a certain 
relation to the consumption of oxygen in respiration; and the quantity of 
oxygen taken up in a given time determines in all seasons, and in all climates, 
the amount of food necessary to restore the equilibrium.” 
A somewhat concentrated supply of nitrogen does, however, in some cases, 
seem to be required when the system is overtaxed; as for instance, when 
day by day, more labour is demanded of the animal body than it is compe- 
tent without deterioration to keep up; and perhaps also, in the human body, 
when under excitement or excessive mental exercise. It must be remembered, 
however, that it is in butcher’s meat, to which is attributed such high flesh- 
forming capacity, that we have also, in the fat which it contains, a large pro- 
portion of respiratory material of the most concentrated kind. It is found 
too, that of the dry substance of the egg, 40 per cent. is pure fat. 
A consideration of the habits of those of the labouring classes who are 
under- rather than over-fed, will show, that they first have recourse to fat 
meat, such as pork, rather than to those which are leaner and more nitroge- 
nous; thus perhaps indicating, that the first instinctive call is for an increase 
of the respiratory constituents of food. It cannot be doubted, however, that 
the higher classes do consume a larger proportion of the leaner meats ; 
though it is probable, as we have said, that even with these as well as pork, 
more fat, possessing a higher respiratory capacity than any other constituent 
of food, is taken into the system than is generally imagined. Fat and butter, 
indeed, may be said to have about twice and a half the respiratory capacity 
of starch, sugar, &c. It should be remembered, too, that the classes which 
consume most of the leaner meats, are also those which consume the most 
butter, sugar, and in many cases, alcoholic drinks also. 
It is further worthy of remark, that wherever labour is expended in the 
manufacture of staple articles of food, it has generally for its object the con- 
centration of the non-nitrogenous, or more peculiarly respiratory constituents. 
Sugar, butter, and alcoholic drinks are notable instances of this. Cheese, 
which at first sight might appear an exception, is in reality not so; for those 
cheeses which bring the highest price are always those which contain the 
most butter; whilst butter itself is always dearer than cheese. 
In conclusion, it must by no means be understood that we would in any 
way depreciate the value of even a somewhat liberal amount of nitrogen in 
food. We believe, however, that on the current views too high a relative 
importance is attached to it; and that it would conduce to further progress 
in this most important field of inquiry if the prevailing opinions on the sub- 
ject were somewhat modified. 
1852. o § 
