THE PIGEON. 227 



205. The strong, hard walls of the gizzard : the bluish 

 tendons, occupying the central portion of its convex right 

 and left sides, and the muscular fibres radiating from the 

 circumference of each tendon to the edge of the organ. 



XL Unravel the intestine by cutting or tearing 

 through the mesentery, and measure its len gth as 

 compared with that of the cjjelome : then cut 

 open the proventriculus and gizzard, the latter by 

 a vertical incision midway between its two convex 

 faces : also cut open portions of the intestine, and 

 observe : 



206. The thick glandular walls of the proventriculus, 

 presenting on their inner surface the well-marked apertures 

 of the gastric glands. 



207. The very thick muscular walls of the gizzard, and 

 its lining of thick, horny, yellow or green epithelium : 

 the small stones with which its cavity is largely filled : the 

 place of entrance of the proventriculus, a wide aperture at 

 its anterior end, and the pylorus, or place of exit of the 

 intestine, a crescentic aperture to the right of the former 

 opening. 



208. The villi, minute filamentous processes of the 

 mucous membrane of the small intestine : seen to advantage 

 only by examining under water, after well cleaning : in 

 the duodenum and proximal portion of the ileum they 

 are comparatively long and closely set, but in the distal 

 portion of the ileum they become shorter and sparser, and 

 towards the end of that division of the intestine pass into 

 longitudinal ridges. 



XXXII. Dissect away the peritoneum and the re- 

 mains of the posterior air-sacs from the kidneys 

 and reproductive organs, taking care not to 

 injure the postcaval vein (§ 215), and, in the 



Q 2 



