ORGANS OP RESPIRATION AND VOICE. 169 



ORGANS OF RESPIRATION AND VOICE. 



ONE order is met with among the Amphibia, namely, that of the 

 Ichthyodea, in which several genera of the family Proteidea or 

 Perennibranchiata, including the Siren, Proteus, and Axolotl, breathe 

 thoughout the whole of life by means both of branchiae and lungs. 

 The remaining Ichthyodea, as the Menopome and Amphiume, respire 

 by gills like the raniform Amphibia and Salamanders, only during 

 their larval or tadpole state. The structure of the Branchiae differs 

 in many respects i'rom that of the same organs in Fishes. They are 

 united in a similar manner to the lingual bone, but are riot appended 

 to the skull as in Fishes. The branchial arches are constituted in 

 the Proteus of three, or, as in the Siren, of four strips of cartilage 

 upon either side, consisting of several pieces, and which are united 

 with the posterior shaft of the lingual bone, and frequently, like in 

 Fishes, are provided upon the surface turned toward the cavity of 

 the mouth with small teeth, while upon the external side they support 

 the fringed gills. The coverlids of the gills are merely membranous, 

 and the complicated opercular apparatus met with in the Osseous 

 Fishes is completely wanting. In the Derotremata, as the Amphi- 

 ume and Menopome, where the external gills are absent, an open 

 fissure exists throughout their whole period of existence. In the 

 larval condition of the Batrachia four cartilaginous branchial arches 

 are found, but these disappear at a later period, and then represent 

 the posterior appendages or cornua of the lingual bone. In this 

 respect the Tailed and Anourous Batrachia exhibit several differ- 

 ences. 



Three external branchiae only are usually found in the Ichthyo- 

 dea and Tadpoles, the posterior branchial arch, when present, 

 supporting no gills. Each gill consists of a long shaft, supporting 

 upon its edges a double row of branchial fringes in the form of sim- 

 ple unbranched filaments, upon which the very fine arteries and 

 veins are so distributed as to form single currents of blood. In rare 

 cases the fringes are ramified, and project into small but broader 

 terminal leaflets. In the larvae of the Salamanders and Tritons the 

 external branchiae are very large, while in the Tailless Batrachia they 

 are more retracted internally, and a small hole conducts from without 

 into the branchial cavity. 



The Trachea is completely absent in the Ichthyodea and some 

 Anourous Batrachia, as the Frog and Toad, in which the rudimen- 



