474 MANUAL OF ZOOLOGY sect, xii 



(hu, hu 1 ), which it depresses. The elevation of the wing is 

 performed, not, as might be expected, by a dorsally placed 

 muscle, but by the sub-clavius (sb. civ), arising from the 

 anterior part of the body of the sternum, dorsal to the 

 pectoralis, and sending its tendon (sb. civ') through the 

 foramen triosseum to be inserted into the dorsal aspect of 

 the humerus. In virtue of this arrangement, the end of the 

 foramen acting like a pulley, the direction of action of the 

 muscle is changed, the backward pull of the tendon raising 

 the humerus. 



Digestive Organs. — The mouth (Fig. 287) is bounded 

 above and below by the horny beaks, and there is no trace 

 of teeth. The tongue (tug) is large and pointed at the tip. 

 The pharynx leads into a wide and distensible gullet (gul), 

 \vhich soon dilates into an immense reservoir or crop (crp) 

 situated at the base of the neck, between the skin and the 

 muscles and immediately in 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 (ptvri) and 

 the gizzard (giz). The proventriculus appears externally 

 like a slight dilatation of the gullet, but its mucous mem- 

 brane is very thick and contains numerous gastric glands 

 so large as to be visible to the naked eye. The gizzard has 

 the shape of a biconvex lens ; its walls are very thick and 

 its lumen small. The thickening is due mainly to the im- 

 mense development of the muscles which radiate from two 

 tendons, one on each of the convex surfaces. The epi- 

 thelial lining of the gizzard is very thick and horny, and 

 of a yellow or green colour : its cavity always contains small 

 stones, which are swallowed by the bird to aid the gizzard 

 in grinding up the food. 



