Observe:
I. Three layers: (a) External Intercostal muscle and mem-
brane, (b) Internal Intercostal muscle and membrane, and
(c) Innermost Intercostal and Transversus Thoracis muscles
and the membrane connecting them.
The intercostal vessels and nerves running in the plane be-
tween the middle and innermost layers of muscles. Subse-
quently, the lower intercostal vessels and nerves occupy the
corresponding morphological plane in the abdominal wall
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