EY THE PEESEDEHT. 
135 
food of the right chemical quality, hut also of appropriate physical 
condition. The chemical usefulness of muscle-making food as 
coarse as that just mentioned is not lost to us. We give it to 
lower animals, and they convert it into what for us is more or 
less tender assimilable meat. As to variation in the power of 
assimilating food possessed by different individuals, that is a 
matter of ill-health rather than of health, and therefore, is outside 
the scope of the present subject. Defective assimilation must be 
treated by the expert in matters of ill-health, that is to say, by the 
practitioner of medicine. Only when assimilation is satisfactory 
will “ good digestion wait on appetite, and health on both.” 
From the laws governing the frame’s income and expenditure of 
bone-making substances and flesh-forming materials, we pass to the 
laws illustrated by the last of the three great classes of food, 
namely, warmth-giving aliments. Most of each loaf we eat; the 
greater part of potatoes; a large proportion of farinaceous puddings, 
pie-crust, and cakes; sugar ; butter and the fat of meat: all these 
are useless for bone-making and more or less useless for flesh¬ 
forming. Their chief office is, apparently, to burn within us 
night and day ; thus maintaining that warmth of the body without 
which we could not exist for a moment. Not more certainly does 
fat or oil burn in a firegrate or lamp and give heat than it burns in 
the human body and gives heat. Further, a given quantity of fat 
or oil, when fully burnt, affords a given quantity of heat, and 
always the same quantity of heat, whether the fat be burnt in a 
stove, a lamp, or the human body. If we burn an ounce of butter 
in an appropriate vessel, in the ordinary way, the whole of the 
heat is evolved in a short space of time, and gives so intense a 
temperature that we speak of it as raising a thermometer to perhaps 
a thousand degrees. If we gradually eat an ounce of butter in 
the ordinary way and thus burn it in the body, we get the same 
total amount of heat from it as before, but that heat is evolved in 
a far longer space of time, and maintains the body during the whole 
of that time at about 98 degrees—the average temperature of the 
body. Not only does fat thus burn in the body, but all the other 
substances just mentioned similarly burn, maintaining the whole 
system at about 98° F. Some of the farinaceous foods mentioned 
may be converted in the body into fat, and this fat may be stored 
within us, occasionally to an inconvenient extent, but it is only 
stored and will certainly during life sooner or later be burned. It 
is only right to add that in place of so much heat some other force 
may be yielded by fuel-like foods—force directly enabling the 
system to perform a certain proportion of its work. 
