442 



ANATOMY OF VERTEBRATES. 



346 



of semilunar valvular folds, of which the lower, f 9 is the l ileo- 

 cecal,' the upper, e, the ' ileo-colic ' valve. A transverse con- 

 striction, d, usually marks the boundary between caecum and 



colon. In the apes and all 

 lower quadrumana the ileo-caecal 

 orifice and valve are circular. 

 The mucous membrane of the 

 caecum and colon is the seat of 

 both intestinal tubules and fol- 

 licles : the latter are chiefly pre- 

 sent in that of the rectum, which 

 is disposed in numerous folds. 

 Although this gut appears 

 straight in a front view, it fol- 

 lows, in Man, the curve of the 

 pelvic cavity, through which it 

 passes, as shown in the side view, 

 fig. 346. The peritoneum is re- 

 flected from its upper third, form- 

 ing the ' recto vesical ' pouch, ib. 

 r, v ; and the rest of the gut is 

 section of Human pelvis, siiowing course of rectum, ^tached bv the ordinary areolar 



CXLVII1". J <f 



tissue to the surrounding part. 

 Anthropotomy accordingly distinguishes, in the rectum, an upper 

 or ' oblique segment,' s, r l : a middle or ' arcuate segment,' r 2, and 

 a ( terminal portion,' r 3 : inclosed at the end by the i sphincter 

 ani,' q, n. 



§ 331. Alimentary canal of Carnivora. — In this group the di- 

 gestive system is adapted, as a rule, exclusively for animal diet. 



The oesophagus is usually 

 wide. The muscular fibres 

 are arranged in an external 

 longitudinal and an internal 

 transverse layer : but, in the 

 Lion, a third layer of longi- 

 tudinal fibres is applied to 

 the inner side of the circular 

 ones at the terminal part of 

 the tube: they are separated 

 from the circular fibres by 

 loose areolar tissue ; and are 

 closely attached to the lining membrane of the oesophagus, 

 which they, here, pucker up into numerous narrow alternating 



Homach of the Lion. 



