474 ELEMENTARY ANATOMY. [LESS. 



The cartilages of Santorini may be confluent in the middle 

 line, as in the Hedgehog and Pteropus. 



The cuneiform cartilages (of Wrisberg) may be more de- 

 veloped than in man, as in the Bear and Dog. 



An extra, interarticular^ cartilage may be developed be- 

 tween the bases of the arytenoids and the cricoid, as in the 

 Hedgehog. 



Vocal cords may be wanting, as in the Porpoise, or the 

 upper cords alone may be obsolete, as in the Sloths and 

 Armadillos. A median air-sac may be developed between 

 the cricoid cartilage and the first ring of the trachea, as in 

 A teles. 



The ventricles of the larynx may be greatly dilated and 

 prolonged upwards so as to come into contact above, and at 

 the same time there may be a pair of extra sacculi opening 

 between the arytenoid cartilages and the glottis, while with 

 these may coexist a median sac, filling an enormously ex- 

 panded os hyoides. Such is the case in the Howling 

 Monkeys (Mycetes). 



A median air-sac may be developed from the thyro-hyoid 

 membrane beneath the epiglottis, extending over the neck 

 and to the armpits, as in some Semnopitheci and Cyno- 

 cephali. 



There may be, as in the Siamang Gibbon, a globular air- 

 sac communicating with the la.rynx by two apertures in the 

 thyro-hyoid membrane. 



The ventricles of the larynx may be distended into 

 enormous air-sacs, stretching over the chest, reaching to 

 the armpits, and sometimes opening one into the other in 

 the middle line of the body, as in the adult Gorilla, 

 Chimpanzee, and Orang. 



When we descend below man's class we see that the larynx 

 may be much more, or but little more, imperfect in structure 

 than it is in any Mammal. 



Thus, in Birds we find thyroid, cricoid, and arytenoid 

 structures, bony or cartilaginous. There may also be in some 

 cases, as e.g. in the Swan, an epiglottis, but this is very rare. 

 More often an epiglottis-like process of the thyroid may be 

 developed. The cricoid may be represented by three pieces. 

 Vocal cords are always wanting. The thyroid has often 

 transversely extended fissures, or defects of solidification or 

 ossification, probably related to the formation of this structure 

 by the coalescence of primitively distinct rings or arcs. 

 Passing below Birds we find that both the thyroid and 



