580 THE INTESTINAL CANAL, BY E. KLEIN AND E. VERSON. 



rectum in the adult it attains a thickness of 3 4 millimeters 

 The proportions are still more remarkable in the newly born 

 child, in which the parietes of the rectum are from 1'3 to To 

 millimeters thick. This thickening is partly independent and 

 proper to itself, being in fact due to the increase of its own 

 muscular layers, but is in part also attributable to extrinsic 

 causes ; the rectum, after leaving the peritoneum, receiving 

 numerous muscular fasciculi from the adjoining parts, and in 

 particular from the nmsculus levator ani. 



The muscular tunics, of which the external here again forms 

 a continuous layer, become in the lowermost parts constantly 

 more and more closely connected with the adjacent tissues ; and 

 as the mucous membrane gradually passes into the external 

 skin, the organic muscular tissue of the intestine blends with 

 the transversely striated muscle in the neighbourhood of the 

 anus. 



The peritoneum also, where it invests the rectum, appears 

 to be thickened, and the submucous tissue, which becomes 

 steadily thicker and denser below, is partly continued directly 

 into the subcutaneous connective tissue of the regio analis, and 

 partly penetrates in the form of bands between the divisions of 

 the musculus sphincter externus. 



MUSCULAR TUBE. The longitudinal fibrous layer of the 

 intestine, which again forms a more continuous layer in the 

 rectum, in consequence of the dilatation of the three ligamenta 

 coli, still exhibits in the upper parts considerable differences in 

 its thickness, suggestive of its previous fasciculated arrange- 

 ment. In the newly born child, at this level, variations occur 

 to such an extent, that in some parts the thickness amounts 

 to 0'23 of a millimeter, whilst in others it does not exceed O06 

 of a millimeter; and similar differences occur in the adult. 

 The muscular bands gradually become extended by lateral 

 expansion, decussate in some parts with the outermost fasciculi 

 of the circular muscular layer (at the valves of Houston), and 

 finally become associated with the innermost fasciculi of the 

 musculus levator ani, which, at first separated from them by a 

 thin layer of connective tissue from the posterior portion of the 

 pelvic fascia, ultimately join directly with them at acute 



