42S Messrs. Allen and Pepys on Respiration „ 
the former is in nearly the same proportion to the latter, as 
azote to oxygen in atmospheric air. 
4. That an animal is capable of breathing a mixture of 78 
parts hydrogen, and 22 oxygen for more than an hour, with- 
out suffering any apparent inconvenience. 
5. That the excitability of an animal is much diminished 
when he breathes any considerable proportion of hydrogen 
gas, or that it at least has a tendency to produce sleep. 
6 . That there is reason to presume an animal evolves less 
carbonic acid gas during its sleeping, than in its waking 
hours. 
7. That the lungs of a middle sized man contain more than 
100 cubic inches of air after death. 
These experiments have been conducted without reference 
to any particular theory, and indeed some of the results 
were so contrary to our preconceived opinions, that we have 
been induced to bestow more than ordinary attention on 
the subject. Confident, however, that all those who repeat 
the experiments with the same care will arrive at the same 
results, we shall rest satisfied with stating the facts, not with- 
out ,a hope that those brilliant discoveries of Professor Davy, 
which have already given us new views of the operations of 
nature, will in their progress furnish us with that explanation 
which it is in vain to expect at present. 
Azote or nitrogen, for instance, has been considered as a 
simple or elementary substance ; it is recognised, however, 
principally by negative properties. Every gaseous fluid 
which will not support life or combustion, which is not ab- 
sorbed by water, nor acted upon by the tests for oxygen, nor 
capable of being detonated with oxygen gas, is generally pro- 
