12 OXYGEN REQUIRED 



when the resistance is not sufficient to arrest the 

 current. 



It is from this point of view, and fi'om no other, 

 that chemistry ought to contemplate the phenomena 

 of life. Wonders surround us on every side. The 

 formation of a crystal, of an octahedron, is not less in- 

 comprehensible than the production of a leaf or of a 

 muscular fibre ; and the production of vermilion from 

 mercury and sulphur is as much an enigma as the 

 formation of an eye from the substance of the blood. 



The first conditions of animal life are nutritious 

 matters and oxygen, introduced into the system. 



At every moment of his life man is taking oxygen 

 into his system, by means of the organs of respira- 

 tion ; no pause is observable while life continues. 



The observations of physiologists have shewn that 

 the body of an adult man, supplied with sufficient 

 food, has neither increased nor diminished in weight 

 at the end of twenty-four hours ; yet the quantity 

 of oxygen taken into the system during this period 

 is very considerable. 



According to the experiments of Lavoisier, an 

 adult man takes into his system, from the atmo- 

 sphere, in one year, 746 lbs., according to Menzies, 

 837 lbs. of oxygen ; yet we find his weight, at the 

 beginning and end of the year, either quite the 

 same, or differing, one way or the other, by at most 

 a few pounds. (1)^ 



What, it may be asked, has become of the enor- 



^ The Numbers refer to the Appendix. 



