1762 HUMAN ANATOMY. 



developmental defects ; {b) the presence in the abdomen of portions of the pelvic 

 organs increasing intra-abdominal pressure ; (/) the habitual ilexion of the thighs on 

 the abdomen in infants, relaxing the tissues about the hernial orifices ; {d ) the ex- 

 treme shortness of the inguinal canal, the internal ring then lying almost directly 

 behind the external ring, so that the canal is about equal in length merely to the 

 thickness of the abdominal wall. The diminution in frequency during childhood is 

 due to the improvement in posture, to the lessening in size of the abdominal rings 

 and to the shortening of the tissues about them, and to the lengthening of the interval 

 between the rings as the ilia grow and incline outward and the internal ring follows 

 them, — i.e., to the formation of the inguinal canal with its valve-like resistance to the 

 protrusion of viscera. The increase in frequency as puberty approaches and is 

 passed is due to the more active habits of life and the assumption of occupations 

 often laborious. It may also be due to a slight extent to the fact that until the pel- 

 vis has fully developed the femoral ring and canal scarcely exist, and that therefore 

 the femoral variety of hernia is rarely found before that time of life. Later in 

 life hernia is still more frequent, although it, like aneurism, lessens in numbers as 

 old age draws on. This is due to the fact that although in both instances the pre- 

  disposing cause — the weakness of vessels or of the abdominal wall — may be said 

 usually to increase when the active period of life is passed, the exciting causes due 

 to occupation and muscular effort diminish with relatively greater rapidity. 



Sex. — Hernia is more frequent in males because (a) the structures connected 

 with the male genitalia are more often the subject of developmental defects {vide 

 i?ifra), and (b) the inguinal canal in the female is narrower (containing only the 

 round ligament) and longer (the distance between the anterior superior iliac and the 

 pubic spines being greater), and for both these reasons offers less opportunity for the 

 descent of viscera. . 



The descent of the testicle and the associated changes, which are often imperfect, 

 sufficiently account for the great frequency of inguinal (92-95 per cent.) as compared 

 with all other forms of hernia in males. 



In females femoral hernia is less common than inguinal hernia. It, is however, 

 relatively more common than in males because (a) m females Gimbernat's ligament 

 {g.v.) is narrower, thus increasing the area of the femoral ring ; and (b) it is weaker 

 and less firmly attached, and accordingly offers less resistance to visceral protrusion. 

 In 100 ruptured persons the percentages as to inguinal and femoral hernia in the 

 two sexes are as follows : male inguinal, 83.5 ; female inguinal, 8.5 ; female femoral, 

 5.9; male femoral, 2.1 (Macready). 



The extent of the influence of a certain shape of the abdomen — with lateral 

 bulgings parallel with and just above Poupart's ligament and extending above the 

 level of the crest of the ilium — is doubtful, but it certainly indicates a laxity of the 

 abdominal wall, and just as certainly is often, as a precedent condition, associated 

 with hernia. 



The almost invariable preponderance of right-sided hernia in all varieties, at all 

 ages, and in both sexes has been variously attributed to (a) the greater bulk and 

 weight of the liver ; (b) to right-sidedness in walking and lying, and to the greater 

 strain on the muscles of the right side caused by "right-handedness ;" {c) to the 

 inclination from left to right of the mesentery of the small intestine as it descends ; 

 (d ) to the greater frequency of incomplete descent of the testis and of a patulous 

 funicular process on the right side ; and (e) to the larger capacity and circumference 

 of the right side of the pelvis (Knox, Macready) as compared with the left, causing 

 a corresponding increase in the size of the right femoral ring. 



External herniae are influenced as to the site of their protrusion by anatomical 

 conditions causing a diminution over certain localized areas in the resistance of the 

 abdominal wall to intra-abdominal pressure. These conditions depend usually upon 

 the necessity for the passage from within out of (a) normal structures such as the 

 spermatic cord {oblique or external inguinal hernia) or the round ligament (the 

 labial \-Ax\(t\.y of obliqne hernia) ; or {b) such as the larger vessels or nerves {njnbilieal, 

 femoral, obturator, sciatic hernice) ; or (r) upon the weakness or absence at given 

 points of some of the components of the abdominal wall, as at the internal inguinal 

 fossa or the supravesical fossa {direct or internal iyigninal hernia), along the linea 



