EXTRACT XXV. B. 

 ON THE SIGMOID FLEXURE OF THE COLON. 



THE sigmoid flexure (see Figs. 1 1 3, 1 1 5), as already implied, 

 represents an anatomical device of the highest functional 

 value, and an evolutionary product due largely to the as- 

 sumption of the erect position by the members of the human 

 race and the consequent necessity for the provision of an 

 automatic or self-acting and regulating alvine, circulatory, 

 and evacuant machinery, whereby the "calls of nature " can 

 be conveniently controlled and organised to meet the neces- 

 sities, amenities, and complex requirements of man's higher 

 individual and social destiny. 



Thus viewed, the sigmoid flexure represents, in a highly 

 conspicuous degree, the anatomical evolution of structural 

 adaptations to changing functional requirements, as these 

 alter and increase, to meet altering generic needs thus the 

 horizontally poised and quadrupedally progressing animal 

 is not " on all fours " with its related erect and bipedally 

 progressing human neighbour, and hence does not display 

 that more elaborate and, so to speak, more finished disposi- 

 tion of its enteric canal, that is to be observed in the latter. 

 This distinction, no doubt, is due to the combined influence 

 of the altered nature and manner of their respective 

 alimentations and the position of their respective alimentary 

 organs, in relation to gravity and the position of the orifices 

 of inlet and outlet of the alimentary and residual materials 

 current in their nutrition ; thus, the nearest mammalian 

 relations of man usually possess excretory orifices at points, 

 generally speaking, superior to or on a level with, although 

 sometimes, from functional necessity, etc., below, the 



