HERNIA (in morbid anatomy). The pro trusion of any viscus from the cavity in which it ought naturally to be contained is termed a hernia, and thus the apparent escape of any part from any of the great cavities of the body may seem to constitute the disease : still, how ever, as the real existence of cerebral or thoracic ruptures rests upon very doubtful authority and is extremely questionable, and as abdominal protrusions are unfortunately equally palpable and frequent, the application of the term is usually limited to them. To this frequency many causes seem to contribute. In the walls of the abdomen there are three remarkable natural openings, or perhaps it would be more correct to say, there are three situations so weak and unprotected that they easily yield and per mit the escape of any viscus that may be di rected against them with even a moderate de gree of force: these are, the umbilicus, through which during fatal life the umbilical cord passes; the inguinal canal, which allows the passage of the spermatic cord in the male, and the round ligament of the uterus in the female ; and the crural ring, which transmits the great bloodvessels to the thigh and lower extremity. The nature of the walls too, which are princi pally composed of muscle, and the condition of the viscera within, loose, liable to change of size and situation, and subject to irregular pres sure by the contractions of these muscular walls, dispose to the occurrence of the disease in any of these situations, where the resistance to such pressure is but feeble. llence hernim are most frequently met with at one of the places al ready mentioned,—the umbilicus and the ingui nal and femoral canals. But there are other situations* at which protrusions may possibly take place, although fortunately they are infre quent, such as, at the side of the ensiform car tilage, at the obturator foramen, at the sacro ischiatic notch, and between the vagina and rectum in the female. It is also evident that if the muscles or tendons of the diaphragm are wounded, some portions of the contents of the abdomen may escape, thus constituting the varieties of ventral and phrenic liernim. Ac cordingly the forms of this disease have been arranged and named from the different places at which they occur,—an arrangement of the greatest practical importance ; for as the struc ture, the size, and shape of each aperture must exert a peculiar influence on the condition of the protruded viscus, on its liability to become incarcerated, on the possibility of its being returned, on the steps to be adopted for this purpose, and above all on the safety and suc cess of an operation should such be necessary, a knowledge of each of these in connexion with hernia is absolutely indispensable.
Besides this division of hernia as to situ ation, there is another of very considerable im portance derived from the nature of the viscus displaced : thus in abdominal ruptures the con tents of the tumour may be intestine alone, in which case it is called enterocele; or omentum alone, the epiplocelc; or both these may be engaged, constituting the entero-epiploccle. There is not a viscus in the abdomen or pelvis, excepting perhaps only the pancreas and kid neys, that has not at one time or another formed the contents of a rupture. The stomach has been partially displaced through the dia phragm, or pushed through the walls of the ab domen: the duodenum has formed part of a ventral or umbilical hernia : the jejunum or ileum are very likely to be protruded in any situation : the ornentum is often displaced, particularly in inguinal herniae at the left side : the large intestines from being more fixed are not so frequently thrust out, yet the ccecum and colon are but too often found among the con tents of a rupture. 1 have seen a large portion of the liver in an umbilical hernia of the infant : Verdiert relates numerous cases of herniae of the urinary bladder ; and Potts mentions one which renders it nearly certain that the ovaria in females may suffer in a similar manner. However, the natural situation of any viscus within the abdomen is but an uncertain cri terion by which to judge of the contents of a hernia in its vicinity. The strangest displace ments have been observed occasionally in the examination of this disease : thus the sigmoid flexure of the colon has been protruded at the right side, and the ccecum and valve of the ileum at the left. In all large and old hernim the parts are dragged out of their proper situations, 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.