Dissection of Sheep^s Head. 259 



with the scissors between the arytenoid cartilages through 

 the tracheal rings and cricoid cartilage. 



The base of the Epiglottis will then be seen to be attached 

 to the upper margin of the thyroid cartilage, the largest of 

 the cartilages of the Larynx, and which consists of two lateral 

 expansions or also, which meet and unite anteriorly at an acute 

 angle, forming a projection answering to the 'Adam's Apple ' 

 in Man. 



The upper Yocal Chords are small and inconspicuous. 

 The Tracheal rings are complete, but not absolutely joined, 

 the division being traceable all down the right side. 



By pressing outwards the mucous lining of the upper part 

 of the Larynx between the Arytenoids and the base of the 

 Epiglottis, a hard substance will be felt holding an antero- 

 posterior direction : this is the Thyro-hyal bone. 



Dissection of the Hyoid Boxes. Without going into 

 the detail of the muscles, the Student should acquaint himself 

 with the position of the series of Hyoid bones, of which the 

 Thyro-hyal is the posterior. 



Turning the side of the head up again, he will find this bone 

 almost underlying the tendinous part of the di- gastric muscle, 

 parallel with which it continues for about an inch ; at this 

 point, and underlying the Hypo- glossal nerve, a joint will be 

 found ; as also what appears to be a single bone (running at 

 right angles to the Thyro-hyal, prolonged a little way down 

 and continuing up towards the last molar of the upper jaw), but 

 which really forms two of the factors of the arch, the downward 

 prolongation being a small round nodule representing the basi- 

 hyal, and the upward prolongation being the cerato-hyal. At 

 the upper end of the cerato-hyal will be found another bone 

 running towards the stylo- hyal ; this is the epi-hyal, and thus 

 the S of the hyoid arch is completed, the top of the S be- 

 ing attached to the Skull, the convexity of the bend support- 

 ing the Tongue, and the return end supporting the Larynx. 



