ORGANIZATION OF REPTILES. 15 



be protruded. In the Serpents it is very long and slender, cleft at the extremity, 

 and can be projected with great rapidity; and like the tongue of some Birds, when 

 drawn within the mouth it is enclosed in a sheath. In Frogs and Toads we find 

 a peculiar arrangement not seen in any other vertebrated animals; the tongue is 

 long, and resembles a valve, the anterior extremity being the fixed point, or that 

 attached to the concavity of the lower jaw, while the posterior extremity is directed 

 towards the glottis, and is cleft and movable. The tongue is here an important 

 organ in obtaining food, for it can be projected suddenly and with great force, and 

 bemg covered with a viscous matter, the prey adlieres to it and is carried to the 

 mouth. 



The Ungual hone varies greatly in form and in the disposition of its parts, not 

 only in the different genera, but in the different species of Reptiles. In all, there 

 is a central portion or body, and several processes named cornua, varying in 

 number, in extent, and in arrangement. This bone is m'-,^.^ed by certain muscles 

 going to the tongue, to the lower jaw and sternum, and in all, its essential function 

 is to support the tongue and facilitate its motions.* 



Pharynx. In general there is no soft or hanging palate to mark the termination 

 of the mouth and beginning of the fauces; nor can we observe any difference of 

 structure in the lining membrane, which, however, presents a number of longitudinal 

 folds that disappear when the organ is distended by food in deglutition. In the 

 AlUgator the velum appears in the form of a semicircular fold, and is sufficiently 

 extensive to cover the entrance of the posterior nares. 



The oesophagus can only be distinguished from the pharynx by its smaller size, 

 and this distinction can only be made when the canal is empty. In Serpents, it is 

 extremely dilatable, allowing the animal to swallow large bodies; and in this class, 

 the folds are most remarkable. In some of the Chelonian anunals there are many 



* Vide Meckel, Deutsches Archiv. fiir die Physiologie, Viert. Band, p. 223, for an accurate 

 account of the lingual bone in the various tribes of Reptiles. 



