(Fig. XIX, 9.) The opening of the appendix into the caecum is situated just below and internal to the junction of the right lateral vertical and intertubercular planes, at the top right-hand corner of the hypogastric region. The surface marking of the caecal orifice of the appendix does not coincide with McBurney's point, which is situated at the junction of the outer and middle thirds of a line drawn from the right anterior superior iliac spine to the umbilicus. This point represents the usual seat of maximum pain on palpation in an attack of appendicitis. The appendix is usually 3 to 4 inches long, and, according to Testut, is in 40 per cent, of cases directed downwards and inwards, overhanging the pelvic brim, whilst in 26 per cent, of cases only is it directed upwards and inwards (towards the spleen). Stress should be laid on the fact that the ileo-caecal valve and the caecal orifice of the appendix are both situated on the postero-internal aspect of the caecum.
The ascending colon passes upwards from the level of the intertubercular plane to the upper part of the ninth right costal cartilage, (Fig. XIX, 10.) the gut there turning on itself to form the hepatic flexure. In its upward course the ascending colon lies almost entirely to the right of the right lateral vertical plane.
The transverse colon extends from the hepatic flexure on the right to the splenic flexure on the left. (Fig. XIX, 11.)
The former flexure corresponds to the ninth costal cartilage, whilst the latter reaches upwards as high as the eighth. In between these two points the gut varies greatly in direction in different subjects. Most commonly the gut passes almost transversely from one side to the other, crossing the middle line at about the level of the second lumbar vertebra. It also crosses the second part of the duodenum, (Fig. XIX, 12.) and lies, therefore, usually above the umbilical plane. In the diagram the two flexures are depicted, but the intervening portion of the gut has been intentionally omitted.
The descending colon passes almost vertically downwards from the region of the splenic flexure to the level of the posterior part of the iliac crest, (Fig. XIX, 13.) below which level it becomes known as the iliac colon. The descending colon lies wholly to the left of the left lateral vertical plane.
The operation of lumbar colotomy is now seldom performed, (Fig. XVII, 13.) but it is nevertheless necessary to indicate the position of the descending colon on the posterior aspect of the trunk. It corresponds in direction to a line drawn vertically upwards to the tip of the last rib, from a point situated 1/2 inch behind the midpoint along the iliac crest between the anterior and posterior superior iliac spines.
Between the termination of the descending colon at the level of the iliac crest, and the beginning of the rectum proper at the level of the third piece of the sacrum, the large gut describes so varied a course that no definite detailed account can be given of its surface marking. It may, however, be briefly described as passing downwards and inwards from the level of the iliac crest, (Fig. XIX, 14.) parallel to Poupart's ligament, as far as the left side of the pelvic brim (the iliac colon). The gut then forms a great loop (the pelvic colon), (Fig. XIX, 15.) which sweeps over to the right side of the pelvic brim, turning on itself to become the rectum at the level of the third sacral vertebra.
A line which unites the two posterior superior iliac spines crosses the spinous process of the second sacral vertebra. (Fig. XVII, 14.)
The rectum begins at the level of the third sacral vertebra, and may be indicated on the surface by drawing in the gut as starting about 1/2 to 3/4 inch below the above-mentioned line, and extending downwards, following the curves of the sacrum and coccyx, to the anal orifice, which is placed about 2 inches below the level of the tip of the coccyx. The dura mater enclosing the spinal cord (see "spinal cord") reaches downwards to the level of the third sacral vertebra. Fig. XVII.
The spinal dura, therefore, terminates at the same level as the rectum begins, a point to be borne in mind in those operations carried out in the sacral region for the exposure of a growth involving the gut in the neighbourhood of the ilio-pelvic and rectal junction.
(Length, 4 1/2 inches; breadth, 2 1/2 inches; thickness, 1 1/2 inches; weight, 4 1/2 ounces).
(Fig. XV, 32.)The two kidneys are obliquely placed in such a manner that the superior poles lie 1 1/2 to 2 inches, and the inferior poles 2 1/2 to 3 inches, distant from the middle line. The left kidney lies at a slightly higher level than its fellow, and the hilum is placed just below and internal to the junction of the transpyloric and left lateral vertical planes; or, in other words, the hilum of the left kidney lies just internal to the anterior extremity of the ninth costal cartilage. The upper pole lies half-way between the sterno-xiphoid and transpyloric planes, whilst the lower pole corresponds to the subcostal plane. The right kidney does not ascend to quite such a high level, and the inferior pole lies opposite the umbilical plane. The hilum of this kidney also lies just below the level of the hilum of the opposite kidney.
(b) Posterior surface marking—Morris's quadrilateral.— (Fig. XVII, 10.) Two vertical lines are drawn at a distance of 1 inch and 3 1/2 inches respectively from the median posterior line, and two horizontal lines are drawn outwards at the level of the spinous processes of the eleventh dorsal and third lumbar vertebrae. In the quadrilateral so marked out, the kidneys are drawn, care being taken to place the long axis of each kidney in the required oblique direction.