550 THE RABBIT CHAP. 



With a scalpel or razor cut across one of the kidneys 

 through the hilus, parallel to the dorsal and ventral faces of 

 the organ, and note the pelvis, and its prolongations the 

 calices, the urinary pyramid, and the cortical and medullary 

 portions. Sketch. Examine also microscopic preparations 

 of injected and iminjected kidney (compare pp. 146 and 537). 



X. Dissect out the lumbo-sacral plexus in the pelvic cavity 

 (p. 532), and then cut through the body just behind the 

 diaphragm ; the abdomen will be no longer required, but 

 you should retain one of the hind-limbs if you wish to 

 examine any of its muscles and joints (compare p. 64). 



E. Dissection of the thorax and neck. 



I. Dissect away the pectoral muscles, cut through all the 

 vertebral ribs of the left side except the last five, at about a 

 quarter of an inch from their junction with the sternal ribs : 

 from the posterior end of the incision thus made, cut down- 

 wards (i.e., towards the sternum) for about an inch, and then 

 forwards through the sternal ribs. Turn forward the flap 

 thus separated and carefully dissect it away from, the under- 

 lying tissues at the anterior end, so as to detach it altogether 

 without injuring the jugular and brachial veins. Note in 

 the thoracic cavity thus laid open : 



1. The pericardium and heart, and the thymus (Fig. 135). 



2. The collapsed lungs : make a small aperture in the 

 trachea and inflate. 



3. The parietal and visceral layers of the pleura and the 

 mediastinum (Fig. 138). To make out the relations of these 

 and of the mediastinal space more accurately, cut away a 

 flap from the right wall of the thorax, as you have already 

 done on the left side, leaving the sternum intact. 



4. The relations of the pericardium, to see which cut 

 through the posterior end of the sternum : separate the 

 mediastinum from the dorsal surface of the bone, turn the 

 latter forwards and remove it : then cut the pericardium 

 open longitudinally, noting the pericardial fluid. 



II. Dissect away the pericardium, the thymus, and any 

 fat about the base of the heart which may obscure the 

 vessels arising from it. Follow out these vessels to the head 

 by clearing away the connective-tissue, fat, &c., by which 

 they are surrounded, but taking care not to injure any of 

 the nerves of the neck. Make out : 



I. a, The left and right ventricles and auricles, and the 

 ramifications of the coronary artery and vein ; b, the two 

 bronchi. 



