THE PIGEON. 221 



bronchi, which pass outwards and backwards to the lungs 



( 181). 



178. The cavity in which the posterior end of the trachea 

 and the bronchi lie is the interclavicular air-sac ( 164), 

 the ventral wall of which is destroyed by the removal of the 

 sternum. 



179. The sterno-tracheal muscles, paired slender 

 bands, easily mistaken for arteries, passing from the ventral 

 side of the trachea outwards and backwards to the inner 

 surface of the sternum. 



180. The epigastric or anterior abdominal vein, a 

 small vessel, taking blood from the great omentum, and 

 passing forwards in the falciform ligament towards the 

 anterior border of the liver (see 253, p. 240). 



181. The lungs, dark-red, spongy bodies, seen by turn- 

 ing aside the heart : they are closely applied to the dorsal 

 wall of the anterior part of the ccelome. 



182. The kidneys ( 214) and the reproductive 

 organs ( 209 213), seen by turning aside the intestines 

 in the dorsal region of the posterior part of the ccelome. 



XXV. Make a median incision through the skin on the 

 dorsal surface of the head, and reflect it to right or 

 left, so as to expose the skull : beginning a little 

 behind the eyes, cut away the thin cranial roof 

 with a scalpel or pocket-knife, taking great care 

 not to injure the brain, which is in close contact 

 with the bone (consult Fig. 58, p. 255) : proceed 

 until the whole of the roof of the skull and the 

 arches of the first two or three vertebrae are 

 removed : when the whole of the dorsal and 

 lateral surfaces of the brain are clear, cut through 

 the spinal cord a short distance behind the 

 brain ; lever up the front of the brain with the 



