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SECT. XVII. PHYSIOLOGY. 133 
cccxrx. In a healthy state, the lungs are supple 
and pliant, and follow the movements of the 
parietes of the thorax, the moment they enlarge 
this cavity. In expiration, they are pressed by 
the parietes of the thorax, because the quantity 
and rapidity of expiration depends on the capacity 
of the thoracic cavity ; the lungs are at the same 
moment relieved from the strain of distention. 
ccexx. In those cases where adhesion has 
taken place between the pulmonary and costal 
pleura, it is conceivable that the thorax may be 
perforated in any part of the adhesion, without 
collapse of the lung of the same side. It is 
only in cases of adhesion, I apprehend, that 
protrusion of a lung, through a wound of the 
thorax, can occur, which some authors say they 
have seen. 
cccxxI. When an opening is made in the chest 
of a dog, the air makes considerable noise while 
rushing into this cavity ; and when the diaphragm 
recoils upon the lungs, part of the air is again 
expelled with a sound like a sudden puff of air 
from the nozle of a pair of bellows. 
cccxx11. Collections of air, either between the 
pleura or under the cellular membrane, are re- 
duced by some vital process; but whether by 
absorption, as alleged by professor Chaussier, or 
by exhalation, or by a combination of both me- 
thods, does not seem clearly established. 
