Arrangement of two pleursB
in front, and their exact
relationship to front wall
of chest.
Anterior mediastinum (posi-
tion, boundaries, and con-
tents).
Triangularis stemi.
Intercostal muscles.
Internal mammary vessels

(perforating branches).
Intercostal vessels and nerves.
Ligaments of sternum.
Bissection of tborax. — Saw through the
sternum just below where it is attached to the first
rib, and again just above where it joins the ensiform
cartilage. Cut through the muscles in the first
intercostal space, as far back as the angle of the ribs.
The muscles of the sixth or seventh intercostal space
may be cut in the same manner, also as far back as
the angla The student must not fail to notice that
by this incision he is dividing the parietal layer of the
pleura as well as the muscles, and therefore cutting
into the pleural cavity. The ribs, from the second to
the seventh inclusive, must be cut through at their
angles with a pair of strong bone forceps. The greater
part of the front and side walls of the chest can then
be removed in one piece.
This plan of removing the whole chest wall at
once will be found to offer many advantages, as it
permits any foul fluid that may have accumulated
in the chest to be readily drained off, and leaves the
constituents of the thorax wall readily available for
dissection.
