384 



ZOOLOGY 



SECT- 



cti.coe crb.h 



front of the sternum. In this cavity the food, consisting of grain, 

 undergoes a process of maceration before being passed into the 

 stomach. From the crop the gullet is continued backwards into 

 the stomach, which consists of two parts, the proventriculus (prvn.) 

 and the gizzard (giz.). The pro- 

 ventriculus appears externally like 

 a slight dilatation of the gullet ; 

 but its mucous membrane is very 

 thick, and contains numerous gas- 

 tric glands so large as to be 

 visible to the naked eye. The 

 gizzard has the shape of a biconvex 



FIG. 1051. Columba livia. Dissection from the right side. The body-wall, with the verte- 

 bral column, sternum, brain, &c., are in sagittal section ; portions of the gullet and crop 

 are cut away and the cloaca is opened ; nearly the whole of the ileum is removed, and 

 the duodenum is displaced outwards, a. ao. aortic arch ; bd. 1, bd. 2, bile-ducts ; b.fabr. 

 bursa Fabricii ; cbl. cerebellum ; coe. right caecum ; cpdm. coprodaeum ; cr. cere ; crb.k. 

 left cerebral hemisphere ; crp. crop ; cr. v. 1, first cervical vertebrae ; di.cce. diacoele ; dnt. 

 dentary ; duo. duodenum ; eus. ai>. aperture of Eustachian tubes ; giz. gizzard (dotted 

 behind the liver) ; gl. glottis ; r/u!. gullet ; Urn. ileum ; i. orb. sp. inter-orbital septum ; 

 Jed. right kidney ; Ing. right lung ; Ir. liver (right lobe) ; na. bristle passed from nostril 

 into mouth ; obi. sep. oblique septum ; o.gl. oil-gland ; pcd. pericardium ; pmx. premaxilla ; 

 pn. pancreas ; pn. b. pineal body ; p.nd. 1 3, pancreatic ducts ; pr. cv. right pre-caval ; 

 prdrn. proctodaeum ; prrn. proventriculus (dotted behind liver) ; pt. cv. post-caval ; ply. b. 

 pituitary body : pug. st. pygostyle ; r. an. right auricle ; r. br. right bronchus ; ret. rectum ; 

 r. vnt. right ventricle ; sp. cd. spinal cord ; spl. spleen (dotted behind liver) ; s. rhb. sinus 

 rhomboidalis ; s. sc,r. syn-sacrum ; st. carina sterni ; syr. syrinx ; th. v. J, first, and th. v. 5, 

 fifth thoracic vertebra ; tug. tongue ; tr. trachea ; ts. right testis ; ur. aperture of left ureter ; 

 urdm. urodasum ; v. (If. aperture of left vas deferens. 



lens : its walls are very thick and its lumen small. The thickening 

 is due mainly to the immense development of the muscles which 

 radiate from two tendons, one on each of the convex surfaces. The 

 epithelial lining of the gizzard is very thick and horny, and of a 



