920 



PERINEUM. 



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 

 aperture much more backwards than they do 

 after 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 

 its bony parietes, but simply from the senile 

 curvature of the spme 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. The 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- 



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 young 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 peritoneum 

 and the anus are still separated by a very 

 trifling interval; but from this period up to 

 puberty the intermediate distance gradually in- 

 creases, pari pawn, with the growth of the 

 pelvis and the developement of the inferior 

 fund us of the bladder. 



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 part 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. 



In the child the sacrum and coccyx present 

 but a trifling curvature, and therefore the rec- 

 tum reaches the anus by a less circuitous route 

 than that just described, and which is the nor- 

 mal condition in the adult; during childhood 

 the inclination backwards of the lower extre- 

 mity of the gut scarcely exists, it possesses but 

 a single curve concave forwards, which, like that 

 of tiie sacrum and coccyx, is but faintly marked, 

 so that the intestine is much straighter in early 

 life than after puberty. In old age the rectum 

 immediately above the anus is sometimes in- 

 flected from side to side so as to assume a 

 zigzag appearance : these lateral inclinations are 

 the result of the enormous enlargement which 

 the bowel occasionally undergoes in the ad- 

 vanced periods of life, its length being actually 

 increased at the same time that its cavity is 

 dilated. 



In the adult subject the rectum is somewhat 

 cylindrical in shape, but it increases in capacity 

 as it descends, and presents a marked dilatation 

 just above the sphincters, whilst the anus and 

 so much of the gut as is embraced by those 

 muscles exhibit a decided contraction. In the 

 child tiie dilatation just described is but little 

 marked, whilst in advanced life it very fre- 

 quently becomes excessive, and is best appre- 

 ciated when the intestine is fully distended with 

 faeces or artificially inflated ; under such cir- 

 cumstances the anterior wall of the rectum is 

 hollowed into a deep depression or gutter, in 

 which the prostate gland and base of the bladder 

 are imbedded, and the bowel swells outwards 

 and forwards upon each side of the prostate, 



