VI.] 



THE COMMON FROG. 



11 



— the OS hyoides continues essentially the same in 

 structure, and even in the adult frog this bone 

 exhibits nothing but a rather wide " body " with two 

 loner and slender "cornicula" and a pair of shorter 

 " cornua." 



Fig. 39. 



Fig. 39.— Diagram of the Larynx of Man, the thyroid cartilage being supposed to he 

 transparent, and allowing the right arytenoid cartilage {,Ar), vocal ligament {U ), 

 and thyro-arytenoid muscle {Tk A), the upper part of the cricoid cartilage (C'), 

 and the attachment of the epiglottis {Ei>), to be seen. C th, the right cricothyroid 

 muscle ; Tr, the trachea ; Hy, the body of the hyoid bone. The right lesser cornu 

 appears as a very small process, extending upwards and backwards from the bodv 

 of the hyoid behind the letters Hy, and in front of the Epiglottis. The light, 

 great cornu is shown extending backwards from the body of the Hyoid and ter- 

 minating beneath the letters Ep. 



FlG. 40.— Extracranial portion of hyoidean apparatus of Dog, front views sk, stylohyal ; 

 eh, epihyal; ch, ceratohyal (these three constitute the "anterior cornu"); bh, 

 basihyal, or "body" of hyoid; th, ihyrohyal, or "posterior cornu." (From 

 Flower's " Osteology.") 



Let us now pass for a moment to the other end of 

 the Vertebrate sub-kingdom. We find in fishes a 

 complex framework for the support of the gills, or 

 structures, by which they effect their aquatic respira- 

 tion. This framework consists of a number of arches 

 (placed in series one behind another) extending on 



