EXCREMENTS AND URINE. 81 



mineral ingredients, moreover, experience in individ- 

 ual cases an increase of quantity, which must, never- 

 theless, be attributed simply to the dust adhering to 

 the provender. In young and still growing animals 

 a considerable diminution takes place in respect of 

 the latter substances, because they need such mate- 

 rial for the enlargement of their bones and other 

 bodily organs. 



Should inquiry be made respecting the form in 

 which the three elements first mentioned are with- 

 drawn from the animal body, accurate experiments 

 have demonstrated that this is effected by the assist- 

 ance of the air inhaled in respiration, in exactly the 

 same manner as by the process of combustion. The 

 vapors and gases escaping by the skin and lungs 

 have precisely the same composition as the steam 

 and gases escaping by the chimney during the com- 

 bustion of wood (vegetable fibre), starch, or similar 

 substances. The changes of non-azotized food (com- 

 posed of carbon, hydrogen, and oxygen), as they oc- 

 cur in the animal organism, may accordingly be re- 

 garded as a slow combustion; and now the source 

 of the warmth we perceive in every animal body, so 

 long as it has life, is no longer an enigma, but a very 

 natural consequence of the process of combustion or 

 digestion. For the quantity of heat which a body 

 evolves during its combustion is always the same, 

 whether this process be briskly or slowly conducted ; 

 only in the latter case it is gradually developed and 

 distributed over a longer space of time. For exam- 



