1220 SURFACE AND SURGICAL ANATOMY. 
formed by the seventh costal cartilages and the lower border of the body of the 
sternum is termed the infrasternal notch. Below the notch, and bounded on either 
side by the seventh, eighth, and ninth costal cartilages, is the infracostal angle, 
which varies considerably according to the shape of the chest ; it is relatively wider 
in the child than in the adult. The lower border of the curve of the tenth costal 
cartilage is easily recognisable, and has been selected by Cunningham as the level 
of the plane of separation (infracostal plane) between the upper and middle abdo- 
minal zones. 
The anterior abdominal wall is limited below by the fold of the groin and the 
erest of the pubes. In a spare muscular subject the recti, the furrows corre- 
sponding to the liner transverse, and the supra-umbilical portion of the linea alba, 
can be readily made out. When the outline of the rectus is not visible the outer 
border may be indicated by a line drawn from the tip of the ninth costal cartilage 
to the mid-point of a line joing the umbilicus and the anterior superior iliac 
spine, and from thence to the pubic spine. In the angle between the outer border 
of the rectus and the ninth costal cartilage, on the right side, is a slight triangular 
depression which overlies the fundus of the gall-bladder. Between the lower part 
of the outer border of the rectus and the prominence above the anterior part of the 
iliae crest, caused by the lower muscular fibres of the external oblique, is another 
slight triangular depression, which corresponds to the lower and narrow part of 
the aponeurosis of the external oblique muscle. 
Close above, and almost parallel to, the inner half of Poupart’s ligament is the 
inguinal canal, traversed by the spermatic cord (Fig. 297, p. 402); the latter can be 
felt to emerge at the external abdominal ring immediately above the pubic spine. 
The external and internal abdominal rings have been fully described elsewhere; the 
former is triangular in shape, with its apex directed upwards and outwards, and its 
base immediately above the pubic crest. By invaginating the skin of the scrotum 
the little finger may readily be passed through the ring into the canal. It is 
to be noted that the neck of an inguinal hernia lies above the pubic spine, 
whereas the neck of a femoral hernia emerges below the inner end of Poupart’s 
ligament, external to the pubic spine. The internal abdominal ring, an opening 
in the fascia transversalis, ies 3} in. above a point a little internal to the 
middle of Poupart’s ligament. The deep epigastric artery may be mapped out by 
drawing a line from a point midway between the anterior superior ilac spine and 
the symphysis pubis towards the umbilicus. The vessel, together with the inner 
third of Poupart’s ligament and the lower part of the outer border of the rectus, 
bounds a triangle known as Hesselbach’s triangle. As the deep epigastric artery 
passes upwards and inwards to disappear behind the conjoined tendon and the 
outer border of the rectus, it lies behind the spermatic cord immediately internal 
to, and below, the internal abdominal ring. The floor of Hesselbach’s triangle 1s 
formed throughout by the fascia transversalis, superficial to which, over the inner 
half or so of the triangle, is the conjoined tendon. An oblique inguinal hernia leaves 
the abdomen at the internal abdominal ring and traverses the whole length of 
the inguinal canal; its coverings are therefore the same as those of the spermatic 
cord, and the neck of the sac lies external to the deep epigastric artery, hence this 
variety of hernia is also termed an external inguinal hernia. A direct inguinal 
hernia, on the other hand, instead of traversing the whole length of the inguinal 
canal, pushes before it that part of its posterior wall which is formed by the floor 
of Hesselbach’s triangle. The neck of the sac, therefore, hes internal to the deep 
epigastric artery, and this variety of hernia may be termed an internal inguinal 
hernia. Tf a direct hernia makes its way through the mner part of Hesselbach’s 
triangle, it derives a covering from the conjoimed tendon as well as from the fascia 
transversalis ; if through the outer part of the triangle, the outer edge of the con- 
joined tendon curves round the inner side of the neck of the sac. To relieve the 
constriction at the neck of the sac, in the case of an oblique inguinal hernia, the edge 
of the knife is directed upwards and outwards to avoid the deep epigastric artery, 
while in a direct hernia the artery is avoided by dividing the constriction in an 
upward and inward direction. In an oblique inguinal hernia the sac les within 
the infundibuliform fascia (fascia propria of the hernia), whereas in a direct hernia 
