SIGMOID FLEXURE OF THE COLON 279 



orifices of inlet, all which is in consonance with the 

 anatomico-physical necessities of their horizontal position 

 and the simpler physiological conditions involved in their 

 case. Man, on the contrary, in consequence, it seems to 

 us, or on account of, his vastly altered position in regard 

 to inlet and outlet levels produced by the assumption of 

 the erect position in his " daily walk," and the involved 

 disturbance in level of these orifices, has thereby begotten 

 a necessity for an altered disposition of his alimentary 

 canal, and so the introduction of specific differences in the 

 manner of providing for and effecting the function of 

 excretion has marked his attainment. Here, then, we 

 contend that we are warranted in claiming the duplication 

 or folding of the lower bowel, known as the sigmoid 

 flexure, as a great mechanico-physiological adaptation of 

 the intestinal tube to meet altered conditions as to 

 anatomical position of the human body and the changed 

 operation of the law of gravitation in relation thereto. 

 Thus, the fascial pelvic structures constituting the floor, 

 instead of merely guarding the posterior aspect and 

 extremity of the body, become a real pelvic floor, on which 

 is supported the superincumbent abdominal viscera and the 

 dependent area through which the great excretory organs 

 effect an outlet, it therefore follows that a great evolution- 

 ary work has been accomplished in the adaptation of means 

 to ends herein necessitated. In this evolutionary sequence 

 of events the adaptation of the intestinal canal to withstand 

 the influence of gravitation by automatically acting mechani- 

 cal means, while leaving the intestinal tube, nominally 

 patent, to convey, as formerly, its contents in obedience to 

 physiological law and necessity, stands out in our estima- 

 tion as one of the most manifest examples in the whole 

 range of later anatomical design. Thus we have seen the 

 alimentary canal converted from a horizontally, albeit 

 zig-zagly, disposed canal, to a perpendicularly arranged 

 tube, v/ithout a fundamentally altered plan that canal, as 

 altered, resting at its lower extremity on the pelvic floor, 

 duplicated or folded, so as to provide an automatic means 

 of preventing overflow, or outflow, while allowing the func- 

 tion of peristalsis to be effected as before, with the super- 

 added advantage of safeguarded, but uninterrupted, alvine 



