367 
t 
blood itself, enables it to support all the secretions, 
and to recruit and maintain the health and stability 
of the system. So long, therefore, as the blood con* 
tinues to move, and the secretory functions continue 
to be performed, so long will carbon be supplied to 
act upon the air ; but when the motion of the blood 
is suspended, or has finally ceased, then carbon is no 
longer furnished, nor is the air any longer changed. 
