162 THE ANATOMY OF YERTEBRATED ANIMALS. 



state, are either external branchiae, combined with lungs, as 

 in the perennibranchiate TTrodela j or lungs only, as in the 

 other JJrodela, the 3atracliia^ the GymnopJiiona^ and, prob- 

 ably, the majority of the Labyrhithodonta, 



In the perennibranchiate JJrodela^ the branchial arches (or 

 some of them) are separated by open clefts (the number of 

 which varies from four to two), throughout life, and three, 

 branched, gills are continued by single stems into the integu- 

 ment, at the dorsal ends of the branchial arches. An opercular 

 fold of the integument, in front of the gill-clefts, attains a 

 considerable size in Siredon (Fig. 58), but does not cover the 

 gills. The branchial arches themselves bear no branchial fila- 

 ments. Other Urodela are devoid of external gills, but (as is 

 the case in Menopoma and Ampliimna) present one or two 

 small gill-clefts on each side of the neck, and are thence called 

 Derotremata. The rest of the Urodela, and all the JBatracMa 

 and Gymnophiona, are devoid of both external gills and gill- 

 clefts, in the adult state. 



In all the Amphibia., a glottis, placed on 



the ventral wall of the oesophagus, opens into a 



short laryngo -tracheal chamber with which two 



t^\~§^\ pulmonary sacs are connected, either directly, 



or by the intermediation of bronchi (as in the 



Aglossa), or by a trachea (as in the Gy^nno- 



Kc.-i//, ii„i \i phio7ia). The walls of the pulmonary sacs 



'are more or less sacculated. In most Arn- 



^''•°^;^^3^ phihia the lungs are equal in size ; but in the 



snake-like Gyrnnophiona, the right is much 

 smaller than the left. In Proteus, the pul- 

 monary blood is not all returned to the heart, 

 '"-S.rTv. some of it entering the veins of the trunk. 

 Aerial resf)iration is effected, in the Artipliibia.^ 

 by pumping the air from the oral cavity into 

 Fig. 59.-The brain of the luno's. To this end the m.outh is kept 



Ran a esculenta, ^ , ^ • -, ,,-,... ^ 



from, above, magni- shut, and ingrcss and egress to the air is given 

 S[Zen'?e'pLi^n:'% ^he nasal passages, which always open 

 or olfactory lobes, immediately behind the vomers, at the anterior 

 tory' nerves; Ha'., P^rt of the roof of the niouth. These passages 

 s^heres^^^l o ^S" being opcn, and the hyoidean apparatus de- 

 thaiamencephaion presscd, the air fills the cavity of the mouth. 

 gbnd, i?i^; l!Tp^ ^^^^ external nostrils are then shut, and, the 

 optic lobes ; G, cere- hyoidean apparatus beino- raised, the air is 



bellum; S. rh, the z.*^ j ,■, -^ ^i .-, i i.-- • x ii i 



fou r th ventricle ; torccd, tlirough the opcn glottis, into the lungs. 

 Mo meduiiii obiou- ^\ AmpMbia possess a urinary bladder, 



