294 ZOOTOMY. 



i6o. The lungs, spongy bodies of a light piiTk colour, 

 situated one on either side of the heart. They will be, by 

 the pressure of the air on their outer surfaces, completely 

 collapsed : to see their actual shape and relations they 

 should be inflated from the tiachea, by making a small 

 aperture in it and inserting a blowpipe. 



1 6 1. The pleura, a shining membrane lining the thorax 

 and forming a double median vertical partition — the medi- 

 astinum — which divides the thorax into right and left 

 pleural cavities, in each of which a lung is contained : 

 the mediastium is seen in the space between the pericardium 

 and the sternum (see § 222). 



XV. Place the animal in the prone position, i.e. with the 

 dorsal surface upwards, first pinning together the 

 reflected abdominal walls to keep the viscera in 

 position : make a median incision through the skin 

 from the snout to about the middle of the thoracic 

 region, and dissect away the skin from the whole 

 dorsal surface of the head and neck. Dissect 

 away the muscle from the anterior region of 

 the neck and posterior region of the head, and 

 find the occipito-atlantal articulation, or 

 place where the skull articulates with the vertebral 

 column. Cut through the occipito-atlantal 

 membrane, which will be seen stretching between 

 the supraoccipital and the arch of the atlas : 

 the anterior end of the spinal cord will be 

 seen, arched over in front of the space by the 

 occipital bone, behind by the atlas vertebra. In- 

 sert the point of a pair of bone-forceps or strong 

 scissors between the cord and the bone, and cut 

 away the arch of the atlas : do the same with the 

 arches of the two or three succeeding vertebrae. 



