HERNIA. 



751 



process of the ilium. As these are but different 

 stages of the same disease, both come under the 

 appellation of hernia by the oblique descent. 

 But, 3, when the viscus has been forced 

 through the parietes immediately behind the 

 external ring, and passes out through that natural 

 aperture only, it is then for obvious reasons 

 termed the hernia by direct descent; and 

 although the external characters of the tumour 

 are not always such as to point out the peculiar 

 nature of this protrusion, yet the relative posi- 

 tion of the intestine with respect to adjacent 

 parts must be somewhat different in these seve- 

 ral cases, a difference that will be found to be 

 of some practical importance. 



The peritoneal sac, as viewed internally in 

 the direction of the iliac and inguinal regions, 

 is described by Scarpa as being divided into 

 two great depressions at each side, the medium 

 of partition being the ligament into which the 

 umbilical artery of the foetus had degenerated, 

 together with the fold of peritoneum raised by 

 that ligament. Of these fossae the superior or 

 external is the larger and deeper; it is that 

 within which the intestines are collected when 

 strongly compressed by the abdominal muscles 

 and by the diaphragm in any violent exertion ; 

 and from it inguinal hernia is most frequently 

 protruded, as the ligament and duplicature of 

 the peritoneum prevent the compressed viscera 

 lodged in this fossa from removing out of it to 

 descend into the pelvis. The situation of the 

 umbilical artery varies considerably: some- 

 times it is close upon the internal border of the 

 internal ring, in other subjects at the distance 

 of half an inch from it, or even more ; but it is 

 always at the pubic side of the epigastric ves- 

 sels. Thus, in its direction upwards and in- 

 wards towards the umbilicus it crosses ob- 

 liquely behind the inguinal canal : all herniae, 

 therefore, by the oblique descent pass out from 

 the external or superior abdominal fossa, while 

 those by the direct are in relation to and are 

 protruded from the inferior or internal. Inde- 

 pendent of this configuration there is nothing 

 in the peritoneal cavity as viewed from within, 

 to determine the occurrence of hernia at one 

 place rather than at another. The membrane 

 is in all parts equally smooth and polished, 

 equally strong,* tense, and resisting. This, 

 however, is not the case with respect to the 

 muscular and tendinous walls of the abdomen, 

 which vary very considerably in density and 

 strength in different situations, and in these 

 qualities dissection shews that the hypogastric 

 or inguinal regions are the most deficient and 

 therefore most disposed to permit of the occur- 

 rence of hernia. 



In prosecuting the dissection from within 

 (which is by far the most satisfactory manner), 

 the peritoneum may be detached by the fingers 

 or by the handle of the knife in consequence of 

 the laxity of the cellular tissue connecting it to 



* The strength of the peritoneum is proved by a 

 curious experiment of Scarpa's. He stretched a 

 large circle of this membrane recently taken from 

 the dead body, on a hoop like a drum, and found 

 it capable of supporting a weight of fifteen pounds 

 without being ruptured. 



the adjacent external structures. The fascia 

 transversal is then comes into view, and in it the 

 aperture termed the internal ring, through 

 which the spermatic cord in the male, and the 

 round ligament in the female are transmitted. 

 This aponeurosis varies in density and thick- 

 ness in different individuals : it is continuous 

 with the fascia iliaca, and is connected with 

 the posterior edge of Poupart's ligament : it is 

 denser and stronger externally, and becomes 

 weaker and more cellular as it approaches the 

 mesial line. Where the internal oblique is 

 muscular, the connexion between it and the 

 fascia transversalis is extremely lax, cellular, and 

 easily separable ; but after it becomes tendi- 

 nous, the union is much more intimate, and the 

 fibres of the one can scarcely be distinguished 

 from those of the other unless by the difference 

 of their direction. In most subjects the internal 

 ring is very indistinct, its size, shape, and direc- 

 tion being in general determined rather by the 

 knife of the anatomist than by nature. So far 

 as the fascia is concerned, the external inferior 

 border of the ring is its strongest part, but its 

 internal edge seems to be the stronger as it is 

 supported by the epigastric vessels, and some- 

 times by the remnant of the umbilical artery. 

 Its size is about an inch in length, half an inch 

 in breadth ; its shape oval ; and the direction 

 of its longest diameter perpendicular or slightly 

 inclining from above downwards and outwards. 

 The position of the epigastric artery with re- 

 spect to the neck of the sac at once points out 

 whether a hernia is by the direct descent or not, 

 for it marks the internal or pubic boundary of 

 the internal ring. This vessel is occasionally 

 irregular in its origin, but in its normal or usual 

 state it comes off from the external iliac before it 

 has reached Poupart's ligament, and conse- 

 quently in that position it lies behind the bag 

 of the peritoneum, which it passes by forming 

 an arch, the concavity of which is directed up- 

 wards. It then appears in front, between the 

 fascia transversalis and the peritoneum, but 

 more closely attached to the former, with which 

 it remains when the membrane is torn away. 

 The vas deferens is seen coming from the pel- 

 vis obliquely upwards and outwards until it 

 reaches the spermatic artery, which, having de- 

 scended from above, nearly in a perpendicular 

 direction, meets the vas deferens at rather an 

 acute angle, the former being to the outside and 

 nearly in front of the latter. These vessels 

 having passed the fascia transversalis disappear 

 by arching round the epigastric artery and en- 

 tering the inguinal canal, and they define the 

 inferior margin of the internal ring. The re- 

 mainder of its border is not so very distinctly 

 marked, partly in consequence of a very deli- 

 cate fascia which is given off from it and passes 

 down a short way on the spermatic cord, where 

 it becomes indistinct and is lost; and partly 

 because the transversalis muscle lying before it 

 renders the view obscure. The internal border 

 of the internal ring is always (as stated by Sir 

 A. Cooper) midway between the anterior 

 superior spinous process of the ilium and the 

 symphysis pubis. 



When a protruded viscus, then, is passing 



