I.] THE FROG. 51 



the mouth to the level of the larynx and examine the 

 laryngeal cartilages. 



a. The laryjigo-tracheal cartilage; an annular tract, 

 embracing the base of the larynx. It sends a spur 

 down into the wall of each bronchus. 



b. The arytenoids. That of the left side will be seen 

 as a hood-shaped mass, surmounting a. and lying 

 within the wall of the larynx. 



Muscular fibres {constrictors) will be seen to pass 

 between a. and b. 



5. Turn the specimen over and remove all that remains 

 of the right half, cutting to the level of the middle 

 line. 



a. The laryngo-tracheal cavity ; spacious above and 

 lined by a soft mucous membrane. 



b. The vocal cords. That of the left side will be seen 

 as a tense fold of the lining membrane, running 

 antero-posteriorly. Note its intimate connection 

 with the arytenoid cartilage. 



c. Examine the relations of the laryngeal cartilages, 

 as seen by following their cut edges. 



d. Strip off the mucous membrane with care, so as 

 fully to expose the cartilages for detailed ex- 

 amination. 



These, and similar cartilaginous structures, may 

 be isolated with ease by maceration in \ per cent, 

 nitric acid solution, the excess of acid being after- 

 wards removed by repeated washings in water. 



F. The Urinogenital organs. 



Dissect from the ventral aspect, proceeding as di- 

 rected in Sect. B. Having laid bare the viscera, re- 



4—2 



