668 



PHYLUM CHORDATA : CLASS AMPHIBIA 



The lungs arise as outgrowths of the oesophageal region 

 of the gut, and are connected with the back of the mouth 

 by a short laryngo-tracheal tube, whose slit-like aperture 

 is the glottis. Each lung is a transparent oval sac, with 

 muscle fibres in its walls. The cavity is lessened by the 



Fig. 383. — Urinogenital system of Fig. 384. — Urinogenital system of 

 male edible frog. — After Ecker. female frog. — After Ecker. 



f.b.. Fatty bodies ; v.c, vena cava ; 

 T., testis ; A'., kidney ; w.d., Wol- 

 ffian duct ; d., cloaca ; BL, bladder. 



uvd.. Opening of oviduct ; ov., ovary ; 

 f.b., fatty body ; K., kidney ; t//., 

 uterus ; Ur., opening of ureters into 

 cloaca (c/.), in front of the openings 

 of the oviducts. 



spongy nature of the internal walls, which form numerous 

 little chambers bearing the fine branches of blood vessels. 

 In respiration the mouth is kept shut, and air passes in 

 and out through the nostrils. A frog will die of asphyxia 

 if its mouth be artificially kept open for a considerable 

 time. When the floor of the mouth is lowered, and the 

 buccal cavity thus increased, air passes in. When the 

 nostrils and the opening of the gullet are shut, and the 



