634 WOUNDS PENETRATING INTO TI1E CHEST. 
from the jugular. A counter-opening was made ten minutes 
after the injection. Immediately after the puncture there issued 
a small quantity of fluid, highly tinged with blood, but it was 
not pure blood. We now separated the lips of the puncture, but 
there only issued from it a red serous fluid. 
This horse was destroyed five or six hours after the injection 
of the blood. W e found a clot at the inferior part of the pectoral 
cavity. It formed a mass which had pressed upon the lung, but it 
was not itself extended like a sheet over the floor of the chest, as in 
the former experiments, probably on account of the manner in 
which the blood had run into the pectoral cavity. In one case ithad 
run gently, and had spread itself over a large surface ; in another, 
it had been driven in rapidly, and in a few seconds, by the piston 
of a syringe ; and ithad escaped by a canula, the orifice of which 
was larger than the diameter of the intercostal arterv. The 
form of the clot, and its situation among the surrounding parts, 
depends upon the manner in which the blood is injected into the 
pleural cavity, and, without doubt, also on the opiantity of blood 
injected. 
We have made a counter-opening immediately after injecting 
blood through a wound made in the superior part of the chest, 
and we observed that a very small quantity of blood issued from 
this counter-opening; although we even pushed back the lung 
with a sound, in order to keep the inferior wound free and open. 
The chest of this horse, killed a little while after the experiment, 
contained a great quantity of coagulated blood. 
There are, then, many causes which prevent the escape of the 
blood through these counter-openings ; the two principal are the 
prompt coagulation of the blood, and the obstacle produced by 
the lung itself pressing against the counter-opening, when air 
would otherwise find its way into the chest through the puncture. 
That ought not to astonish us, when w 7 e know that the lung can 
form a kind of hernia across a costal wound, and which proves 
that the lung is not a passive organ in the act of the entrance 
of the air during respiration. We have already had occasion to 
relate, that when a canula was introduced into the pleural sac, 
in spite of the introduction of air into the chest, the lungs dilated 
themselves to such an extent, as to rub against the extremity of 
the canula, and to become excoriated, in consequence of the 
friction at the time of inspiration. 
