CAVITY. 



505 



exist during life, when the viscera of the abdo- 

 men are under the influence of the action of 

 its walls, for then the direction of the superior 

 mesenteric artery is so little downwards and so 

 much forwards that it cannot be said to exert 

 any pressure upon the intestine; yet it is 

 remarkable that in many cases of ruptured 

 intestine, the seat of the rupture has been a 

 very short way below the continuation of the 

 duodenum into the jejunum. The inferior 

 portion of the duodenum rests upon the vena 

 cava and the aorta, and is in contact with 

 these vessels by its posterior wall. The 

 inferior margin of this intestine descends to 

 very near the bifurcation of the aorta, leaving 

 no more than from one-half to three-fourths of 

 an inch interval. We notice, moreover, in 

 this region the obliquity of the mesentery, 

 the arterial and venous, nervous and lacteal 

 ramifications existing between its laminae and 

 the mesenteric glands or ganglions connected 

 with the lacteals, which ganglions are often 

 very few and much atrophied in old subjects. 

 The convolutions of the small intestine are 

 covered in front by the omentum, and are very 

 closely in apposition with each other : hence 

 they become ' matted together 'by the lymph 

 effused in peritonitis, and hence, too, in per- 

 forations, effusion of the intestinal contents 

 by no means necessarily takes place. The 

 looseness of the intestinal convolutions and of 

 the mesentery by which those convolutions are 

 tied to the spine, admits not only of their 

 being liable to frequent introsusception, but 

 also of being strangulated by the twisting of a 

 knuckle of intestine. For the same reason it 

 is that we find this intestine forming most 

 of the hernias which protrude from the various 

 regions of the abdomen. The small intestine 

 occupies the whole central umbilical region, 

 extending likewise on either side into the lum- 

 bar regions and downwards into the pelvis. 

 Thus it forms a considerable mass interposed 

 between the anterior and posterior abdominal 

 walls, and it is easy to conceive how, during 

 an irregularly distended state of the intestine, 

 violence applied to the abdomen in front can 

 cause a rupture of a part of it without occa- 

 sioning any solution of continuity in the wall 

 of the abdomen. 



The laminae of the mesentery pass back- 

 wards and outwards along the sides of the 

 spine, and entering the lumbar regions become 

 continuous with the right and left mesocolons. 

 By their divergence in front of the spine they 

 form a triangular enclosure, the basis of which 

 is formed by the bodies of the vertebrae. In 

 this space we find the aorta, and lower down 

 the primitive iliac arteries, the commencement 

 of the thoracic duct, the receptaculum chyli, 

 and several tributary lymphatics and lacteals 

 with their ganglions, the vena cava ascendens, 

 and the left renal vein, the lumbar arteries and 

 veins, and many nervous ramifications from 

 the sympathetic, and more on the sides the 

 lumbar ganglia of the same nerve; here also 

 we notice the fibrous insertions of the crura 

 of the diaphragm, and the anterior common 

 ligament of the vertebrae. Each lamina of the 



VOL. I. 



mesentery, as it passes outwards, crosses over 

 the ureter lying on the p.soas muscle, and the 

 spermatic artery with the accompanying veins, 

 and some of the musculo-cutaneous branches 

 of the lumbar plexus, and having entered 

 the lumbar region, covers the right and left 

 colons, forming, at its reflections on and off 

 the intestine, the mesocolons. Each of these 

 portions of the colon lies very nearly con- 

 nected to the posterior wall of each lumbar 

 region, having only the lower portion of the 

 kidney, with its surrounding adeps, interposed 

 above. In some instances a mesocolon does 

 not exist, and the colon is bound down to the 

 posterior wall of the lumbar region, so that 

 the posterior surface of the intestine uncovered 

 by peritoneum is in direct contact with the 

 quadratus lumborum muscle or the kidney, 

 having only cellular membrane or fat inter- 

 vening, and this occurs much more frequently 

 at the left than at the right side : hence the 

 not uncommon occurrence of lumbar abscess, 

 or renal abscess, or calculi being discharged 

 into the colon, and so finding their way out by 

 stool. The proximity too of the portions of 

 the colon to the ureters serves, as Velpeau has 

 remarked, to explain how pins, or beans, or 

 pieces of lead find their way into the bladder 

 and become the nuclei of calculi there, 

 or being impeded in their progress through 

 the ureter, the calculous matter concretes 

 around them in that canal. In confirmation 

 of this explanation, he relates a case which 

 occurred at La Pine". A pin, the head of 

 which was still found in the colon, in which 

 it had excited considerable ulceration, had 

 passed also into the ureter, so that a calculus, 

 of which the pin formed the axis, projected 

 partly within and existed partly without the 

 canal of the ureter.* Whether the mesocolons 

 exist or not, the right and left colons are in 

 general so fixed in situ, that they rarely form, 

 the contents of a hernial sac. 



Hypogastric region, The central portion of 

 this region is occupied by the continued con- 

 volutions of the small intestine. The right iliac 

 region is in general entirely or almost entirely 

 occupied by the ccecum, which sometimes has 

 a mesocoecum and sometimes not. In the 

 latter case, a little reticular cellular membrane, 

 and the fascia iliaca, are all that separate the 

 intestine from the surface of the iliacus in- 

 ternus muscle. Beneath the fascia the ilio- 

 scrotal and the inguino-cutaneous nerves are 

 seen passing outwards to their destination. The 

 internal iliac artery and vein lie along the inner 

 margin of the psoas muscle, covered by a thin 

 fibrous expansion, which is a process from the 

 iliac fascia, and deeply seated between the 

 psoas and iliacus internus muscles is the ante- 

 rior crural nerve. The external iliac arteries 

 are crossed at their origin by the ureters, and 

 along their course a few glands may be found 

 either at the sides or in front. This region is 

 one of great interest to the pathologist, in con- 

 sequence of the frequent occurrence of disease 



* Velpeau, Anat. Chir; t. ii. p. 175. 

 2 L 



