12G 
EXTRACTS FROM FOREIGN JOURNALS. 
fact, from which the clinic may derive much profit, and shall de | 
pend for my statements upon dissections, histological observations! 
and a few experimental facts, to all of which I shall refer. 
1st, Dissections. — (a) When the abdominal cavity of a horse 
is opened for examination of the condition of the posterior face 
of the diaphragm, this is seen, very depressible, powerfully 
stretched, and pushed forward by atmospheric pressure. Every 
one knows that in these conditions the external face of the lung 
rests directly upon the internal face of the ribs. But if, by an 
opening through any of the inter-costal spaces, air is allowed tc 
enter the chest, the pressure being then equal upon both surfaces 
of the lungs, this organ shrinks down by reason of its elasticity, 
and the diaphragm, at first concave backwards, becomes at once 
flabby and soft, in consequence of the equality of the pressure od 
both surfaces. 
The same procedure with the ox, or any other of our domestic 
animals, gives different results. But half of the diaphragm 
shrinks down, being that of the side on which the chest has beer 
opened. And this is the case because the two pleural sacs remain 
independent; because the mediastinum is not perforated. 
For years I have observed, in the horse, the same phenomena 
viz.: the flabby condition of one side only of the diaphragm, 
after the consecutive opening of the abdominal and then of the 
thoracic cavities. How can we explain this fact, unless by ad 
mitting that the mediastinum is not perforated in the subjects! 
where I have observed it ? 
(p) Very thin and delicate in its normal condition, the tnedij 
astinic septum is, in most cases, much exposed to be torn undeii 
the influence of an accidental mechanical cause, however slight in 
appearance. 
This is easily demonstrated when, as in the experiment be 
fore mentioned, air is allowed to enter slowly one of the pleura 
sacs through a facetted tube. In this case the unilateral slacking 
of the diaphragm will be obtained with so much more facility 
according as the facette will have been slowly opened. A 
fortiori , this will fails every time the thorax is opened widely by 
the sudden removal of several ribs. 
