Practicum VI. The Larynx and Tongue. 41 



21. The Cartilages of the Larynx. Cut and tear off the small 

 muscles upon the ventral aspect of the larynx and note that it consists 

 mainly of two cartilages, the CRICOID caudad, resembling an enlarged 

 tracheal ring, and the THYROID cephalad, larger and more irregular. 



a. Work the thyroid to and fro and note that it has considerable 

 mobility upon the cricoid. 



b. Medisect the trachea and larynx with the scissors upon both the 

 dorsal and ventral sides. Note that the cricoid is a complete ring, wider 

 at the dorsal side. Also that upon its cephalic margin, at either side of 

 the meson, is perched a small cartilage, the ARYTENOID. 



' 22. The Vocal Bands. From the arytenoid cartilage to the thyroid, 

 near the root of the epiglottis, extends a fold or ridge or shelf of mucosa, 



the VOCAL BAND. 



a. The common name, vocal cord, is misleading ; a fold of mucosa is supported by 

 fibrous tissue. 



23. Action of the Vocal Bands. Hold either half of the trachea 

 and cricoid firmly. Tilt the thyroid ventrad and note that the band is 

 rendered more tense ; tilt the thyroid dorsad and the band is relaxed. 

 Move the arytenoid from side to side and note, when the two are tilted 

 mesad, that the vocal bands are correspondingly approximated. 



a. With a fresh, entire specimen, if a tube is tied in the trachea and the larynx com- 

 pressed somewhat so as to approximate the bands, blowing through the tube will produce 

 a vocal sound on account of the vibration of the free margins of the bands. 



b. If time permits make an enlarged drawing of themesal aspect of 

 the larynx ; compare PI. XVII. 



24. Removal of the Tongue. Pass a scissors-blade from the mouth 

 caudad into the pharnyx and cut first on the right side and then on the 

 left ; unless the hyoid bone has been previously dissected out it will be 

 transected. 



25. The Lingual Papillce. At the tip and base they are simple and 

 FILIFORM, short and closely set at the tip, longer and scattered at the 

 base ; in PL XVII they are not named or very distinctly shown. On the 

 longer intermediate region are the horny, sharp and recurved ODONTOID 

 PAPILLAE ; with a lens may be traced the transition between them and the 

 filiform. At various points but especially near the middle of the tongue 

 are the blunt FUNGIFORM PAPILLA. A little caudad of the middle are 

 about half a dozen CIRCUMVALLATE PAPILLA, arranged as a V with its 

 open end toward the tip ; each may be described as a fungiform papilla 

 encompassed by a circular trench and wall. At the margin near the base 

 are six or eight papillae set like a fringe. The tonsils are not very distinct 

 in the cat. 



26. Transect the Tongue. Note its muscular mass, the mesal 

 rhaphe (seam) and the thick dorsal mucosa. 



27. The Palates. On the roof of the mouth note that the HARD 

 PALATE, between the teeth, presents 6-8 transvers RUG^;, ridges of papillae, 

 with other papillae, less regularly placed, in the intervals. There is a 

 mesal papilla of a different shape just caudad of the interval between the 

 incisors. The SOFT PALATE is smooth. 



28. The Eustachian Tube. With the scissors cutaway the soft 

 palate, exposing the postnasal cavity. At either side is an oblong orifice, 

 straight or sligrhtlv crescentic, the orifice of the EUSTACHIAN TUBE lead- 



o o * * 



ing to the tympanum or middle ear. 



