264 
ESSENTIAL CONSTITUENTS OF HERNIA, 
The essential constituents of a rupture are:— 
(1) The opening in the abdominal wall through which the viscus has 
left the abdominal cavity, and which may either he a normal opening 
like the umbilicus, or one abnormally dilated, as the inguinal canal 
sometimes is, or a rupture in the abdominal coats, without solution of 
continuity in the skin. 
The rim of this orifice is termed the hernial ring. Its form and size 
vary greatly. Sometimes it will only admit the little finger, but in large 
animals it may be the diameter of a man’s fist. Sometimes it is round, 
sometimes oval or slit-like. In umbilical and inguinal herniae it is lined 
with peritoneum. In fresh ventral herniae the edges of the ring are 
formed by the abdominal coats. 
(2) The hernial swelling, which may vary from the size of a hazel 
nut to that of a man’s head or more, consists of the portion of protruded 
viscus, the hernial “contents,” and its coverings, the hernial “sac.” 
The latter is divided into neck and base. The hernial sac consists of 
skin and subcutis, the latter usually thickened, sometimes of layers of 
muscle and abdominal fasciae. Under certain circumstances other coats 
may exist, as, for instance, in inguinal hernia, the tunica vaginalis 
communis and the scrotum. Such special coverings are also termed 
accessory coats of the hernia. 
The sacs of umbilical, inguinal, and femoral herniae, and those whose 
openings consist of abnormally dilated physiological apertures, are 
lined with peritoneum. In those produced by tearing of the abdominal 
walls, the peritoneum is usually divided ; the internal organs may then 
lie under the subcutis, and only be covered by the latter and the skin. 
The contents consist either of a loop of intestine or of omentum 
constituting respectively enterocele or epiplocele. Only very occasion¬ 
ally are other internal organs like the stomach (gastrocele) or liver 
found in the hernial sac. Sometimes the sac also contains a serous fluid 
(hernial fluid). 
In reducible ruptures the contents lie free in the sac, and may be 
returned to the peritoneal cavity (reposition, taxis) ; but sometimes the 
hernial contents and sac become adherent to one another, and complete 
reposition can only be effected after division of the attachment. This 
forms irreducible hernia. The irreducible character may also be due to 
strangulation or other causes, like excessive distension of the protruded 
portion of intestine by hard masses of faeces. 
Diagnosis. A hernia is seldom difficult to recognise, provided it be 
reducible. In such case it has the following characteristics:— 
(a) It is free from inflammatory symptoms (especially pain), is soft, 
elastic, and compressible, that is, it may be diminished by pressure. 
{b) It varies in size from time to time : coughing or severe exertion 
