HERNIA. 



739 



and their appearances on dissection and rela- 

 tive positions are often such as no one from 

 anatomical knowledge alone could ever have 

 suspected to be possible. 



In all forms of abdominal hernia excepting 

 those only which immediately supervene on 

 penetrating wounds, the contents of the rupture 

 are lodged within a pouch or bag termed the 

 hernial sac, which is formed of the peritoneum. 

 This membrane lines the entire cavity so per- 

 fectly and completely that nothing can pass out 

 from it without the membrane also participating 

 in the derangement and being pushed out before 

 the displaced viscus. Once formed, this sac 

 is rarely capable of being replaced or returned 

 into the cavity of the abdomen ; never unless 

 the hernia is small and recent, and " the cel- 

 lular substance accompanying it and the sper- 

 matic cord through the ring has not lost its 

 natural elasticity and contractility." * Many 

 surgeons have doubted the possibility of such 

 an occurrence at any period, f but the fact has 

 been demonstrated by dissection, and still more 

 forcibly by the circumstance of the hernia 

 having been thus strangulated within the ab- 

 domen when the sac has been returned along 

 with it. However, as I have said, the sac when 

 once formed is rarely capable of being replaced, 

 nor does it long remain in this abnormal situation 

 without undergoing some change in its patho- 

 logical condition a change which it is not 

 always easy satisfactorily to explain. In small 

 herniae that have recently come down, the struc- 

 ture of the sac differs in nothing from that of 

 the abdominal peritoneum ; and if the rupture 

 is not reduced or kept up by a truss, it will pro- 

 bably increase in size without any remarkable 

 alteration of tissue, for the membrane is ex- 

 tremely distensible, and will accommodate 

 itself to any quantity of contents. But, if the 

 hernia is carefully kept up, there can be no 

 doubt that the sac will gradually contract and 

 seem to rise up and approach the opening 

 through which it originally passed, so that, 

 although its cavity is never completely oblite- 

 rated, it is palpably diminished in size, and in- 

 capable of receiving and retaining the same 

 quantity of contents it originally held. Some- 

 times in old and neglected herniae the sac 

 seems to become so thin that the peristaltic 

 motion of the intestines within it has been 

 clearly perceived : this most frequently occurs 

 in umbilical hernia, and is one of the reasons 

 why this form of rupture was supposed not to 

 have been enveloped in a sac at all. Again, on 

 the contrary, in old herniae also, and particularly 

 where bandages have been worn to support or 

 compress the tumour, it seems to become very 

 thick, strong, and tense, and is said to have Veen 

 met with as tough and as thick as cartilage. 

 But in the great majority of instances these 

 changes are rather apparent than real, and 

 though doubtlrss the structure of the sac is no 

 longer exactly that which it possessed before 

 protrusion, the alteration is not so great as 



* Scarpa on Hernia, translated byWishart, p. 68. 

 t See Louis, Mem. de 1'Acad. Roy. de Chir. 

 torn. ii. p. 486. 



some writers have supposed. It was the 

 opinion of Scarpa that an old hernial sac is in 

 reality but slightly if at all thickened, and that 

 the apparent thickening is caused by the con- 

 densation of the cellular tissue external to and 

 around it. And here I may remark that diffe- 

 rences of opinion as to the altered structure of 

 the sac may have arisen from a difference of 

 accuracy and minuteness in examination, either 

 during the progress of an operation or after 

 death. We shall find hereafter that the normal 

 anatomy of the parts connected with hernia is 

 largely indebted to the knife of the anatomist 

 for the shapes of the different openings, the 

 division and enumeration of the different layers 

 of fascia, and many other points; but in the 

 morbid anatomy of the disease the same patient 

 investigation and the same accuracy of descrip- 

 tion has not been so uniformly observed, and 

 hence our knowledge of the latter part of the 

 subject as compared with the former is by no 

 means so defined and exact. 



Where a rupture has been a long time down, 

 it is not probable that the intestine shall thus 

 remain in an abnormal situation without occa- 

 sionally suffering from inflammation, and hence 

 adhesions between it and the sac are by no 

 means unfrequently formed : the same effect 

 may be produced^ by accidental violence, or 

 from the latter cause the sac may be ruptured 

 and its contents left lying under the usual 

 coverings independent of the peritoneum. 

 This is another of the cases in which a hernia 

 has been supposed to exist without the invest- 

 ment of a sac. 



The peritoneal aperture leading from the 

 cavity of the abdomen into that of the rupture 

 is narrow, and is called the neck of the sac : its 

 dimensions as to length, however, vary with 

 circumstances. As long as the communication 

 is open and free between the two cavities, all 

 that portion of peritoneum which is placed 

 between them and corresponds to the canal 

 through which the rupture has passed, may be 

 termed the neck, and thus in inguinal hernia 

 may be an inch, and in crural half an inch in 

 length. But when the protruded parts are 

 strangulated, the little circle only around which 

 the compression directly operates is more pro- 

 perly entitled to the appellation, and its extent 

 is seldom greater than two lines. When the 

 neck of the sac of a very recent hernia is viewed 

 from the cavity of the abdomen, the peritoneum 

 in its vicinity is seen thrown into slight folds or 

 plaits, which appear to be prolonged down wards 

 into the tumour; but on slitting open the neck, 

 I have never seen this appearance within it, the 

 membrane there being smooth, rather whiter and 

 more opaque, and evidently thicker and more 

 unyielding than elsewhere. If such a hernia 

 in the living subject has been reduced and kept 

 up by a truss, the nock gradually contracts 

 under the pressure, an.!, iis diameter with re- 

 spect to that of the ring tnrough which it has 

 passed is altered to a degree that is of the 

 greatest importance in the event of another pro- 

 trusion, for it will be shewn hereafter that such 

 a diminution of size greatly predisposes to the 

 occurrence of strangulation. It is also possible 



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