ding to the line of gravitation.

Now, though the above-mentioned circumstances be anatomically true
respecting dropsical effusion within the general peritonaeal sac and
that of the ovary, there are many urgent reasons for preferring to all
other localities the line P Z, as the only proper one for puncturing the
abdomen so as to give exit to the fluid. For though the peritonaeal
ascites does, according to the position of the patient, gravitate to
either side of the abdomen, and displace the moveable viscera on that
side, we should recollect that some of these are bound fixedly to one
place, and cannot be floated aside by the gravitating fluid. The liver
is fixed to the right side, 11, by its suspensory ligaments. The
spleen occupies the left side, 12. The caecum and the sigmoid flexure of
the colon occupy, R R*, the right and left iliac regions. The colon
ranges transversely across the abdomen, at P. The stomach lies
transversely between the points, 11, 12. The kidneys, O, occupy the
lumbar region. All these organs continue to hold their proper places, to
whatever extent the dropsical effusion may take place, and
notwithstanding the various inclinations of the body in this or that
direction. On this account, therefore, we avoid performing the operation
of paracentesis abdominis at any part except the median line, P Z; and
as to this place, we prefer it to all others, for the following cogent
reasons--viz., the absence of any large artery; the absence of any
important viscus; the fact that the contained fluid gravitates in large
quantity, and in immediate contact with the abdominal walls anteriorly,
and interposes itself between these walls and the small intestines,
which float free, and cannot approach the parietes of the abdomen nearer
than the length which the mesenteric bond allows.

If the ovarian dropsy form a considerable tumour in the abdomen, it may
be readily reached by the trocar and cannula penetrating the line P Z.
And thus we avoid the situation of the epigastric vessels. The puncture
through the linea alba should never be made below the point, midway
between P and Z, lest we wound the urinary bladder, which, when
distended, rises considerably above the pubic symphysis.

Amongst the many mechanical obstructions which, by impeding the
circulation, give rise to dropsical effusion, are the following:--An
aneurismal tumour of the aorta, A, or the innominate artery, [Footnote
1] F, may press upon the veins, H