This theory, which is founded on a sound basis, is not
opposed to the preceding; on the contrary, it adds to it,
since the two forces are acting in the same direction; the
first forces the diaphragm upward while the other com-
presses it downward; they act together with the same result.
On the contrary, this theory, which has for its point of
departure a negative pressure, seems to be opposed abso-
lutely a priori to the following which has for its basis a posi-
tive pressm-e.
Theory of flattening of the diaphragm, either through posi-
tive pressiu"e of gas (Maingot), or by the pressure of effusion
(Bernard). This theory is especially defended by Maingot.
Rist and Bernard identify themselves with it. It is open
to discussion. It is easy to see how the condition is brought
about in the course of artificial pneumothorax. Barjon
and P. Commont have studied this.
First, it is quite certain that there may be found in
the pleura very strong pressures ( -j- 10 -|- 15 and even
-f 28 -|- si in one case) without there being any flattening
of the diaphragm; and that this complete flattening may
be seen with much less pressure ( 4- 4 -|- 6 in another case).
It is just as evident that the "movement of balance" is
lacking in a great number of cases of pneumothorax with
very positive pressure. Something else is therefore the
cause. Bar j on has established these facts many times but
four cases only of pneumothorax studied with P. Courmont
wiU be quoted, indicating the pressure in the course of the
successive interventions.
These four observations were selected especially because
they represent perfectly the different stages of detachment
and the increasing progress of pulmonary collapse.
