THE PIGEON. 217 



abdominal sacs : to see them the edge of the sternum must 

 be slightly raised. 



161. The great omentum, a sheet of membrane, 

 loaded with fat, which covers the contents of the abdomen ; 

 by carefully lifting it the posterior air-sacs will be better 

 displayed. 



162. Some of the abdominal viscera (liver, intestine, 

 &c.) can also be seen at this stage of the dissection, but are 

 best examined later (§ 171, &c.). 



XXII. Carefully dissect away the crop from the 

 anterior surface of the sternum and pectoral 

 muscles, taking care not to injure the inter- 

 clavicular and prebronchial air-sacs (§ 1 64) : make 

 a longitudinal incision through either of the great 

 pectoral muscles close to the carina sterni, — the 

 incision should be about half an inch deep at the 

 anterior end of the carina, gradually diminishing 

 in depth as it is continued backwards, and must 

 be made with considerable care, so as not to 

 injure the subclavius muscle (§ 166): continue 

 the incision forwards, gradually separating, the 

 pectoralis major from the furcula, and from the 

 posterior end of the incision continue it outwards 

 so as to separate the muscle from the corpus 

 sterni : when these attachments, together constitut- 

 ing the origin of the pectoralis, are cut through, 

 the muscle will come away quite easily from the 

 underlying parts : reflect it outwards, taking care 

 not to injure the pectoral vessels (§ 168) or the 

 axillary air-sacs (§ 165), and note : 



163. The distal portion of the gullet, passing backwards 

 from the crop, of which it looks like a middle lobe, to reach 

 the body-cavity. 



