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. 



1 80. 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 



