DISSERTATION ON THE ATMOSPHERE. 
167 
air differs little, if at all, in weight. The well-known energy 
of oxygen would have led us to expect no trivial results from 
its activity; but though entering and leaving the body to 
such an extent, no physical change manifests itself. 
The chemical power of oxygen has not, however, been 
checked, much less stifled, but had exercise to the full. 
Otherwise, it might be asked, What has become of the 
weighty and voluminous additions to the system in the 
shape of food? They cannot be supposed to have been 
eliminated from the body in the excreta, since experiment 
shows them to bear away but a tithe of the material con- 
sumed. Moreover, the nature of the discharged products 
afford proofs of a radical change in their nature and conse- 
quent properties. From a healthy and well-balanced system 
it would be further found, that the excrements consist 
mostty, if not entirely, of compounds that possess no nutri- 
tive value. The function of the inhaled air, or, more strictly, 
its constituent oxygen, is here indicated. It lies in trans- 
forming the varieties of food into products available not 
merely for strengthening, but to some extent constituting 
the living body; in removing the waste and worn-out tis- 
sues, in generating vital warmth, and in other ways pre- 
serving activity among all parts. So much may be ad- 
mitted, although, as will be subsequently seen, many views 
may be taken as to the modus operandi. The chemical 
examination of respired air shows a constant recurrence in 
the products exhaled into the external atmosphere. The 
expired ingredients are carbonic acid and water. The prime 
elements to vegetable life are carbonic acid, water, and 
ammonia. We have here discovered a perennial source of 
the two first. They are accompanied by matter capable of 
yielding the third, but we will trace the source of ammonia 
a little farther. 
Conceive an individual deprived of food. For a while the 
heart’s pulses continue to beat, rightly indicative of life, 
because atmospheric air, as ever, passes to and fro ; but no 
longer finding nicely assimilated food wherewith to satiate 
its affinity or appetite, oxygen, with resistless energy, gnaws 
the vital tissues, starvation advances with constant quicken- 
ing step, by-and-by the brain feels as if it were very dust, 
and through various stages of delirium the act closes in the 
agonies of death. It is by no means necessary to abstain 
entirely from food in order to participate in such changes ; 
they are always taking place, although, under wise regu- 
lations, to a very limited extent, but in every case, so that 
ere long death happens from sheer exhaustion. 
( To be continued .) 
