920 
capacity is so limited that the viscera which 
occupy the pelvis of the adult are mostly con- 
tained in the abdominal cavity of the infant. 
The straits of the pelvis have each of them 
likewise an aspect different from that of the 
adult; in the child the superior aperture looks 
much more directly forwards, and the inferior 
peeved much more backwards than they do 
puberty. These peculiarities are inherent 
in the infantile pelvis: they are independent 
of any inclination in the vertebral column, and 
they must therefore modify considerably the 
direction of the pelvic axes during the early 
years of growth. 
In the old subject again the superior aperture 
is once more directed forwards as in the infant, 
. whilst the inferior aperture inclines backwards ; 
at this period of life, however, the change in the 
pelvis arises not from any intrinsic alteration in 
ats bony parietes, but simply from the senile 
curvature of the spine above, added to the ha- 
bitual flexion of the hip and knee-joints below, 
so constantly observed in the aged individual. 
To understand the course of the rectum and 
the urethra, as well as the relations of the base 
of the bladder, the anatomist must study these 
parts within the pelvis, since it is impossible 
to display them satisfactorily in the ordinary 
dissection of the perineum; much assistance 
may be derived from preparations affording a 
side view of the pelvic viscera, and one of the 
most useful is an antero-posterior section carried 
through the middle line and dividing the ure- 
thra, prostate gland, bladder, and rectum, &c., 
after these organs have been moderately dis- 
tended and hardened by alcohol. 
Rectum.—tThe portion of intestine which 
belongs to this region commences at the great 
cul-de-sac of the peritoneum and terminates at 
the anus. It is perfectly devoid of any serous 
investment, and presents considerable varieties 
in size and direction in different subjects. The 
age and the habits of the individual are found 
to exert a remarkable influence upon its course 
and dimensions, and accidental variations in 
the line of reflection of the serous membrane, 
which create corresponding changes in the 
depth of the perineum, are occasionally ob- 
served even in the adult, and ought to be 
taken into account by the operator. 
The great cul-de-sac of the peritoneum is 
usually about three-and-a-half inches distant 
from the anus, so that, making allowance for 
the curved course of the intestine, we may 
estimate the length of the perineal portion of 
the rectum in the adult at somewhat less than 
four inches. In forming this estimate, the 
condition of the urinary bladder as regards its 
distension should not be overlooked, for when 
that reservoir is empty and contracted, the rec- 
tum receives an extensive serous investment, 
and at such times the cul-de-sac of the perito- 
neum approaches the anus perceptibly, whilst 
under the opposite condition (that of repletion) 
the bladder displaces the serous membrane par- 
tially, carrying its cul-de-sac upwards towards 
the abdomen. Individual varieties, irrespec- 
tive of these changes in the bladder, are, how- 
ever, of constant occurrence, and in many in- 
PERINEUM. 
stances the rectum in the adult is covered by 
serous membrane anteriorly to within two inches 
of the anus, the bladder being at the same 
time fully distended. In the youre subject 
the peritoneum stretches very far downwards 
along the surface of the bowel, and at birth 
it very generally covers the front of the rectum 
to within one inch of the anus; at the age of 
five years the cul-de-sac of the peritoneam — 
and the anus are still separated by a very — 
trifling interval; but from this period up to — 
puberty the intermediate distance tes in- 
creases, pari pussu, with the growth of the 
pelvis and the developement of the inferior 
fundus of the bladder. 4 
At its commencement the perineal portion of 
the rectum runs obliquely downwards and for- _ 
wards, this direction it maintains as far as the 
prostate gland, but it there alters its course and 
turns slightly backwards to terminate at the — 
anus. Superiorly it presents a slight curva- 
ture concentric with that of the sacrum, so 
that the anterior surface of the gut is there — 
slightly concave, and its posterior surface 
slightly convex from above downwards: infe- 
riorly, however, the curvature of the intestine 
is reversed ; it appears as it were to turn round 
the point of the coccyx to gain the anus, and 
therefore the convexity of the lower of the 
gut is directed forwards whilst its concavity 
looks backwards. This curved course of the 
rectum ought to be borne in mind by the sur 
geon in his attempts to introduce instruments 
into its interior. ‘y 
In the child the sacrum and coceyx present 
but a trifling curvature, and therefore the rec- 
tum reaches the anus by a less circuitous row 
than that just described, and which is the nor- 
mal condition in the adult; during childhoos 
the inclination backwards of the lower extre. 
mity of the gut scarcely exists, it Lara 
a single curve concave forwards, which, like tha 
of the sacrum and coccyx, is but faintly markec 
so that the intestine is much straighter in early” 
life than after puberty. In old age the rectut 
immediately ibocs the anus is sometimes ii 
flected from side to side so as to assume 
zigzag appearance: these lateral inclinations at 
the result of the enormous enlargement whi 
the bowel occasionally undergoes in the a@ 
vanced periods of life, its length being actua 
increased at the same time that its cavi 
dilated. 7 
In the adult subject the rectum is somet 
cylindrical in shape, but it increases in caps 
as it descends, and presents a marked dilatat 
just above the sphincters, whilst the anus 4 
so much of the gut as is embraced by thi 
muscles exhibit a decided contraction. In) 
child the dilatation just described is but li 
marked, whilst in advanced life it very 
quently becomes excessive, and is best ap; 
ciated when the intestine is fully distended ¥ 
feces or artificially inflated; under such 
cumstances the anterior wall of the 
hollowed into a deep depression or gutter, | 
which the prostate gland and base of the blade 
are imbedded, and the bowel swells outwa 
and forwards upon each side of the pre 
