ALIMENTARY CANAL OF BRUTA. 449 



by the vertical longitudinal section in fig. 352., appears a mere 

 linear, slightly sinuous, tract, with a dilatation near the pylorus, 

 due to the valvular protuberance of the upper wall projecting 

 toward that aperture. But, when the pyloric cavity is bisected 

 transversely, its area presents a crescentic figure, owing to the 

 protuberance formed by the thicker muscular tunic, h, and the 

 more abundant submucous elastic tissue, i, in the upper parietes. 

 The lower longitudinal plica?, which commence on the cardiac 

 side of the intercommunicating aperture, give a longitudinally 

 ridged character to the inner surface of the cavity. 



/ 



This character is changed near the pylorus for a reticular 

 rugosity : the pylorus, when viewed from the duodenal side, pre- 

 sents a crescentic form, with the horns of the crescent directed 

 upward. The lining membrane of the duodenum soon becomes 

 smooth. This intestine is suspended on a broad fold of peritoneum, 

 and is continued into the jejunum without being tied by a con- 

 traction of the mesentery to the vertebral bodies. The ileum 

 dilates rapidly into the colon which commences without a caecal 

 projection. The greatest circumference of the duodenum is 

 2i inches : the calibre of the intestinal canal gradually contracts 



O * 



to a circumference of 1 inch 9 lines at the jejunum, and recovers 

 a circumference of 3 inches near the end of the ileum. The 

 colon, within 3 inches of the ileum, has a circumference of 

 9^ inches ; and has decreased to a circumference of 6 inches, 

 where it forms the rectum, about 9 inches from the anus. 



The inner surface of the duodenum and jejunum is smooth, 

 offering no villi to the naked eye. A few short and narrow 

 longitudinal folds of the lining membrane, not parallel to but 

 following one another, begin to appear in the ileum : these are 

 succeeded bv one or two longer longitudinal folds, which are soon 



*> C* 



followed by one extending continuously throughout the rest of the 

 ileum, along the side of the gut opposite the attachment of the 

 mesentery : this fold is from 2 to 3 lines in breadth, is narrowest 

 where the canal has been most distended, but is not obliterated by 

 the utmost dilatation of the gut : it is a permanent single longi- 

 tudinal production of the vascular lining membrane, and forms the 

 chief characteristic of the lower half of the small intestines in 

 the Myrmecophaga jubata. In this part of the canal there are 

 patches of glandular agminataB from 1 to 2 inches long, and with 

 intervals of about 1 foot. The transition of the ileum into 

 the colon is effected by a rapid increase of diameter, viz. from 

 1 inch to 21 inches; by a slight thickening of the muscular 

 coat ; by the appearance of a few transverse ridges or very low 



VOL. III. G G 



