96 ANATOMY OF THE RABBIT 



scalenus muscle passes over the first rib to the cervical 

 vertebrae.) 



(c) The vertebral ends of the ribs will now be transected. 

 Insert the fingers of the left hand under the ribs and with the 

 cartilage knife cut through the lateral musculature to the ribs in 

 a straight line from between the first and second ribs (the first is 

 later to be broken and left in situ as a land mark) almost even 

 with the dorsal surface of the thoracic cavity (which is deter- 

 mined by digital exploration, and lies about even with the costal 

 border of the iliocostal muscle, 59a) to the caudal margin of the 

 thirteenth rib, or two cm. farther caudad than this. In com- 

 pleting this incision it will be necessary to use bone cutters 

 (preferably heavy scissors type) to cut through the ribs. (A 

 heavy pair of "Wiss" j'jyi inch shears having blades with two- 

 inch cutting edges has served the writer for twenty years.) 

 The second and third ribs are cut first and the others in suc- 

 cession including the last. After the ribs have been cut it is 

 necessary to transect the diaphragm so that the section of the 

 thoracic wall can be flexed onto the abdomen where it will be 

 entirely out of the operator's way and may be returned to its 

 original position at the end of the laboratory period. 



(d) Beginning at the region of the xiphoid process reflex the 

 mass of excised ribs and transect the diaphragm leaving about 

 two cm. of its costal insertion attached to the reflected section 

 of the thoracic wall. Continue this incision dorsad through the 

 crus of the diaphragm (Fig. 28, CD) to the aorta. Be certain 

 to get the form and relations of the diaphragm well in mind, 

 for besides being an important motor organ of respiration it is 

 a most important landmark and bears relations to several other 

 organs and structures. 



A. THORACIC VISCERA 



The contents of the thoracic cavity should be studied in 

 situ, that is, as they lie without their position and relations being 

 disturbed noticeably. 



