132 ANALYTIC SECT. XVII. 
parietes; when an opening is made into one 
division of the chest, the air rushes between the 
pulmonary and costal pleura, with a force which 
the expansibility of the lung occupying the 
wounded cavity, cannot resist, and the lung 
consequently collapses. 
cccxvi. Notwithstanding the collapse of one 
lung, respiration can continue in the remaining 
sound one; but if both sides of the chest are 
perforated, asphexia necessarily ensues. Perfora- 
tion of the mediastinum, after one lung has 
collapsed, is attended with the same consequence, 
cccxvi. The force with which the lungs col- 
lapse, has been shown by Dr. Carson to be equal 
to a column of water of seven inches, in a bullock. 
His experiments prove, that the lungs must be 
always subject to a mechanical distending force, 
while the cavity of the thorax is entire. 
cccxviul. Haller concedes a contractile power 
to the bronchi and air-cells of the lungs; and 
argues, that it co-operates in the expulsion of the 
air in expiration. Asthma is an irresistible proof 
of the existence of such a power in the lungs; 
but it also demonstrates, that a contractile power, 
so far from facilitating respiration, is a serious 
impediment to it. Contraction of the air-cells 
would, obviously, oppose the admission of air — 
into the lungs, and prevent them from expand- — 
ing, when the muscles of inspiration enlarge 
the cavity of the thorax. 
