129 
EXTRACTS FROM* FOREIGN JOURNALS. 
i “ ’ “ 
manipulations of the preparation; whether they were natural, or 
existing previous to the manipulations for the histological exami¬ 
nation—they always have the same characters, viz., they are 
endothelial lacerations , and not natural openings, such as those 
which are observed in the great omentum. 
In this last serous surface, the endothelium shows no separa¬ 
tion, howsoever tine it may be. It is continuous with itself all 
over; its cells are polygonal all over, and present circular edges 
everywhere. 
j From these facts I am brought to the conclusion that the 
openings of the posterior mediastinum are of recent existence, and 
probably are generally artificial. However, as those histological 
examinations are only limited, I am not prepared to deny any 
other explanation of their formation. 
3d, Experiments on the Living Animal.— I have several 
times tried to demonstrate by experiments the distinct separation 
of the two pleural sacs, but I have succeeded only once. The other 
trials have for various reasons failed. 
On the 17tli of February, 1884, I marked with a pair of scis¬ 
sors, upon an old subject for desection, the curve of inferior dull¬ 
ness of the chest, on both sides of that region. Five liters of dis¬ 
tilled water, at a temperature of —|— 30 degrees, were then, very 
slowly and with the greatest care, injected into the left pleural 
sac. During the injection, the subject was kept quiet, and strug- 
; gled very little. After the injection, percussion was made on 
)oth sides of the chest. On the left side, the line of dullness was 
‘aised eight centimetres; curved at first, it had become horizontal. 
Jn the right side the level dullness remained the same. The in- 
ected liquid then remained in the left pleural sac. This condi- 
j don lasted a little more than an hour. 
After a short time the animal was moved in order to see 
whether, under the influence of the injection the rupture of the 
oediastinum had taken place. Percussion on both sides of the 
best showed; the left , a lowering of the horizontal line of dull- 
} iess > three centimetres. It still remained horizontal. On the 
'igh t side the original curve was the same, auscultation on that side 
j ;iving the respiratory murmur, while it was absent on the other. 
