CLASS AMPHIBIA 



479 



at rest. They are long and powerful. The five toes are con- 

 nected by a web, making the foot an efficient swimming organ. 



The skin is smooth and loose ; it contains large black pigment 

 spots and a lesser amount of green and golden pigments. The 

 skin consists, as in other vertebrates (Fig. 347), of two layers, an 

 outer epidermis and an inner derm-is. It is furnished with a large 

 number of mucus glands which secrete the fluid that makes the 

 surface of the body 

 slimy, and a smaller 

 number of poison 

 glands, which secrete 

 a whitish fluid of use 

 probably for defen- 

 sive purposes. 



General Internal 

 Anatomy. The 

 body of the frog is 

 supported by a bony 

 skeleton, is moved 

 by muscles, and 

 contains a well-de- 

 veloped nervous 



FIG. 409. Diagrammatic transverse section of 

 the body of a female frog, to show relation of peri- 

 toneum (broken line) to viscera. Ao, aorta; 

 Ds, dorsal subcutaneous lymph space; G, intestine; 

 IV C, inferior vena cava; A" : kidney; LS, lateral 



, -re ,1 i i .1 K C, interior vena cava; yv. Kiuiiey; L,J, laieia 



system. the body- suhcutaneous lymph space . NC , spinal cord, 



wall IS slit open in n,n, nerves; Od, oviduct; Of, ovary; S, great dorsal 



the ventral middle lymph space; 

 line from the 

 terior end of 



subcutaneous lymph space; i, 2, 3, mesenteries sus- 

 pending the intestine, ovaries, and oviducts. The 

 skin is represented by a thick black line. (From 

 Bourne.) 



pos- 

 the 



body to the angle 

 of the jaw, the organs in the body-cavity or coelom will be 

 exposed. 



The heart lies within the sac-like pericardium ; it is partially 

 surrounded by the three lobes of the reddish brown liver. The 

 two lungs lie one on either side near the anterior end of the ab- 

 dominal cavity. Coiled about within the body-cavity are the 

 stomach and intestine. The kidneys are flat reddish bodies 



