540 CARDINAL OBJECTS 



What then becomes of the surplus oxygen ? 

 Does it unite with hydrogen, as supposed by 

 Crawford, Lavoisier, Cuvier, Dulong, and 

 Despretz ; or with the blood, as maintained by 

 Edwards, and many other physiologists ? Muller 

 thinks it may combine with the blood, giving it 

 a bright arterial hue, but not with hydrogen, 

 because Collard de Martigny found that aqueous 

 vapour was exhaled from the lungs of animals 

 when deprived of oxygen. But this objection is 

 not well founded ; for if 25 per cent, of the oxygen 

 consumed by a healthy man in 24 hours, (which 

 is about 45,000 cubic inches, or 2 Ibs. in round 

 numbers,) were to unite with hydrogen, it would 

 make only 9 oz. of water ; whereas it is known 

 that from 18 to 20 oz. are exhaled from the lungs 

 in that time. Nor does the fact stated by Ma- 

 gendie, that the exhalation is increased by in- 

 jecting warm water into the veins, affect the 

 question, which must be decided by ascertaining 

 the relative proportions of hydrogen in arterial 

 and venous blood. 



If ever we shall be enabled to reduce the 

 phenomena of life to the certainty of fixed prin- 

 ciples, it must be accomplished by ascertaining 

 the elementary composition of organized bodies, 

 and the changes they undergo at every stage of 

 their developement ; what is added to our food, 

 during its conversion into chyme, chyle, and 

 blood ; what changes are effected on the atmos- 



