i68o HUMAN ANATOMY. 



a circle of smaller dilatations just below the line of demarcation, in the region that 

 is reckoned as skin, but is practically puckered into tlie anus. There are communi- 

 cations between the two systems, some of which pierce the muscular coat. 



Lymphatics. — The principal lymphatics of the rectum, after joining the 

 lymph-nodes situated along the superior hemorrhoidal veins, pass to the sacral 

 glands on the front of the sacrum. In the lower part of the bowel a very rich plexus 

 is found, under the skin around the anus, which drains into the superior internal 

 inguinal glands, and a still richer one inside, which at the lower part is concentrated 

 on the columns of the rectum, but few vessels lying in the pouches. A considerable 

 system of lymphatics exists also in the muscular layer. Most of those of the inside 

 of the anus run to a few small lymph-nodules discovered by Gerota ^ on the back 

 of the muscular coat of the rectum, distributed with the branches of the superior 

 hemorrhoidal artery. 



Nerves. — The nerve-supply of the rectum includes both sympathetic and 

 cerebro-spinal fibres. The former are derived chiefly from the inferior mesenteric 

 and the pelvic plexuses, accompanying the superior and middle hemorrhoidal 

 arteries respectively. The cerebro-spinal fibres are contributed by the second, 

 third, and fourth sacral nerves. The skin around the anal orifice is supplied by the 

 inferior hemorrhoidal branch from the pudic nerve. 



Growth. — At birth the rectum is tubular and generally relatively small. We 

 do not remember to have seen a well-marked ampulla at that period. At least 

 frequently the anal canal is very long, — about i cm. The transverse folds of the 

 rectum are apparent in the latter months of pregnancy. We have found an ampulla 

 with a circumference of 13 cm. (5 in. ) at three years. In the same specimen the valves 

 were well developed, and, except in size, it resembled the rectum of the adult. 

 The peculiarities of the infantile sacrum have their effect on the course of the rec- 

 tum, which is necessarily straighter than in the adult and does not run so far forward 

 in front of the coccyx. 



PRACTICAL CONSIDERATIONS : THE LARGE INTESTINE. 



The Caecum. — This part of the large intestine may remain undescended in its 

 fcetal position in the left hypochondrium, at a point above and to the left of the 

 umbilicus, the ileum opening directly into it in this locality ; or it may be found in 

 the right hypochondrium just belpw the liver, or at any level between that and its 

 normal situation. The caecum is rudimentary in man and other meat-eating animals, 

 being much more capacious and of greater functional importance in the herbivora. 



The caecum is larger, more distensible, and more superficial than any other 

 portion of the large intestine, and more mobile than any other portion except the sig- 

 moid. On account of its mobility it is selected for the operation of iliac colostomy 

 when that operation is done on the right side. 



As a result of the inspissation of the intestinal contents, which first occurs here, 

 it is a common seat of fecal impaction, or of distention by gases arising from fermen- 

 tation. The increase in numbers of the intra-intestinal pathogenic bacteria due to 

 impaired inhibiting power, which, as we descend the gut, first becomes marked in 

 the lower ileum, continues in the caecum. As in the former situation, where it prob- 

 ably aids in determining the localization of typhoid and tuberculous lesions, so in 

 the caecum, in conjunction with fecal accumulation, or with disturbance of circulation 

 from distention, such augmentation adds to the frequency and severity of catarrhal 

 inflammations and of stercoral ulcers, which are found oftener here than elsewhere. 



Fecal concretions (the formation of which is favored by intestinal catarrh just 

 as is that of renal calculi by catarrhal pyelitis) are often found in the caecum, and 

 undoubtedly by mechanical irritation favor here, as they do in the appendix, epi- 

 thelial necrosis and subsequent infection. 



In the erect position gravity aids in bringing about these pathological condi- 

 tions, since the caecum, having no mesentery of its own, and yet completely covered 

 by peritoneum (so that it is never anchored to the posterior parietes or to the iliac 

 fossa by areolar tissue), depends upon its attachments to the colon and ileum to hold 



' Arch, fiir Anat. und Entwicklng., 1895. 



