THE RABBIT 20/ 



(c) Remove a ring of the trachea about half way down. 

 Is it the same structure throughout? Draw the end view. 

 What is the advantage of this structure? Of what value 

 is the cartilage in the respiratory system? Cut a piece of 

 the lung tissue as thin as possible (with microtome, if there 

 is one in the laboratory; if not, with razor) and study under 

 the low power of the microscope. Do you find both air tubes 

 and blood tubes? Explain. Draw. 



( 1 1 ) Vocal Cords and Voice. — (a) Study the larynx. 

 Note its situation in the throat. From the ventral side 

 note the epiglottis, a movable membraneous cartilage at the 

 top. Behind is the thyroid, a heavy circular cartilage ex- 

 tending almost around. On the ventral side find the cri- 

 coid, a flat thick cartilage in between the ends of the thyroid ; 

 and behind are the lobes of the arytenoid cartilage. Draw 

 dorsal and ventral views, of larynx. 



(b) Look down into the larynx and see the voice box, 

 in which can be distinguished a pair of membraneous vocal 

 cords. Where are they attached? How are they tight- 

 ened and relaxed? Locate the muscles that do this. For 

 what are these cords used? Make diagram representing 

 them open and also closed. Compare voice box with that 

 of bird. (See page 182.) 



III. The Nervous System. — (i) Remove the kid- 

 neys and the muscles of the interior of the back, looking 

 for white cords, or nerves, which may be found near the 

 vertebral column. Do you find a nerve cord on either side 

 with occasional attachments to the spinal cord? These 

 constitute the sympathetic nervous system. It is connected 

 with ganglia in different parts of the body, the largest of 

 which is the solar plexus in the region of the stomach. 



