ORGANIZATIONOFREPTILES. 29 



sioned by the rushing of the air through the glottis. Some of the Sauria, as the 

 AlHgator, can produce a very loud noise; in this animal the ligaments of the glottis 

 are free and strong, the larynx extending above them on the outer side, like a sac. 

 The voice is most perfect in Frogs and Hylas; in these the vocal chords are large, 

 prominent, and free; the larynx is short and wide, without an epiglottis, though 

 the posterior extremity of the valve-like tongue is supposed by some Naturalists 

 to perform the office of one.* In the male Frogs, we find sacs on each side of 

 the lower jaw, under the ear; in the Hylae, there is a single sac under the throat; 

 these are distended with air when the animal croaks. In these animals, as in some 

 Birds, the voice is only heard at one season of the year; and in the Frogs it is 

 generally, though not invariably, guttural and unpleasant; but some of the Hylse 

 or Tree-frogs have a clear metallic sound, not wholly without sweetness. 



Nervous System. — All the organs hitherto described, as well as the functions 

 they perform, concur to produce one great end, the maintenance of organic life; 

 the apparatus for this effect is perfect, and most of its operations are carried on 

 without the knowledge or consent of the animal. Nature has not submitted 

 operations of such vital importance as respiration, digestion, circulation, &c., to 

 the influence of any causes that depend on the mental or bodily state of the animal, 

 which is liable to frequent change; these phenomena are effected secretly and 

 unconsciously, but constantly. The parts subservient to vegetative life form the 

 basis on which is erected a system of more noble organs, those that elevate the 

 animal above plants, or one animal above another, those organs on which depend 

 sensation, perception, and voluntary motion. 



The whole nervous system may be divided into a central and a peripheral por- 

 tion; the spinal marrow and the brain making the central part, the nerves of the 

 body constituting the other portion. 



* Rudolphi, Grundriss der Physiologic, Zweit. Band, 375, thinks the epiglottis only useful 

 in directing the current of air from the extensive nasal cavities to the glottis, in higher animals; 

 these being wanting in Reptiles, there is consequently no occasion for an epiglottis, and none 

 exists. 



