SECRETAIiy'S REPORT. 1<20 



ohscunty which formerly involved this suhject completely cleared 

 away, yet we may easily learn as much as will serve intelligently 

 to guide our action. Eminent chemical physiologists will tell us, 

 that ..nimal heat is generated and sustained by a process not differ^- 

 ent in kind from tliat by which we warm our rooms, or obtain heat 

 for any of the other purposes of every-day life. To this end, we 

 burn fuel ; and fuel, whether it be wood, coal, or something else, is 

 composed largely of carbon, which, in the process of combustion, 

 combines with oxygen, forming carbonic acid gas, and as a coiise- 

 qncnce of the combination^ heat is evolved. 



Careful experiments have shown conclusively, that the amount of 

 heat thus evolved, corresponds to the quantity of oxygen which enters 

 into combination with the combustible matter, be it carbon, hydrogen, 

 or something else. This can be measured, and we find, too, that 

 the result is the same, whether the combination takes place so rapidly 

 as to produce intense heat, or so gradually that there is no appear- 

 ance of fire at all. The essential point is the combination of oxygen, 

 with the combustible matter ; when this takes place, whether slowly 

 or rapidly, heat is evolved. 



Let us next inquire, what is food, and what becomes of it when 

 eaten ? Take, for instance, the case of an ox fed upon hay, roots 

 and grain. Without going into the minute details of analysis as to 

 their ultimate elements, we find the proximate constituents of these 

 articles of food to consist of, first, albumen, gluten, casein, &c., 

 which are composed of nitrogen, carbon, hydrogen and oxygen. 

 These mainly go to form muscle, cartilage, &c , sfnd are familiarly 

 known as the flesh-forming principles. We also find another class 

 of alimentary substances composed of the same ultimate elements, 

 with the only, but important, difference of being mimfs the ni- 

 troE^en. These are starch, sugar, gum and others. They are 

 known by the generic name of elements of respiration, or familiarly 

 called the heat-producing principles. They are thus called, because, 

 when absoibed in the process of digestion, they are conveyed in the 

 blood to the lungs, there to be exposed to the action of atmospheric 

 air; and duiing the exposure, the carbon combines with the oxygen 

 of the air, and passes away from the lungs as carbonic acid gas 

 mixed with the expired air. (A portion of the hydrogen also com- 

 bines with oxygen theie, and passes away as watery vapor.) Con- 

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