324 Effa Funk Muhse. 



Literature. The skin and the skin glands of Batrachians have 

 been written about very extensively since 1840, when Ascherson 

 dealt with the skin glands of the frogs. The family Ranidae and 

 the families of Urodela have since furnished the favorite species 

 on which work has been done. The skin of the common toad, or 

 the glands contained therein, has in only a few instances been made 

 the subject of a structural study. The toad has been dealt with 

 alone (Eckhard, '49, Eainey, '55, Calmels, '83, Weiss, '99, Bristol 

 and Bartelmez, '08) or incidentally as one of a series of Batrachians 

 (Bolau, '64, Leydig, '67, Schultz, '89, Seeck, '91). With but very 

 few exceptions, the many investigators have been of the opinion that 

 there is present in the cutis of the species of Batrachians dealt with, 

 more than one kind of gland. There is also a diversity of opinion 

 regarding the structure of what is known from the description or 

 classification to be an equivalent type of gland. 



General Description of the Skin. 



Unevenness. As compared with other Batrachians, the adult toad 

 is very warty over its dorsal surface, and there is a general un- 

 evenness over the whole body. Microscopic examination of mounts 

 of the molt, and of prepared sections from various regions of the 

 body, further emphasize the great diversity of elevations in the 

 surface covering of the animal. 



Causes. Numerous gland sacs are located in the cutis, each with 

 a duct passing to the surface of the epidermis, where a distinct 

 opening is visible. At many places in the dorsal skin of the toad, 

 the glands are grouped, producing the so-called warts. (Figs. 9, 

 12-14, 21-24.) The skin lies on a more or less even, unimpression- 

 able surface, the muscles and bone or cartilage, and since the glands 

 can make little or no impression on them, most of the expansion 

 due to these many gland sacs, is outward. The unevenness of the 

 skin is further caused by the presence of elastic fibers in the cutis. 

 The part played by these fibers is evident from two observations. 

 If a piece of skin is cut from any region of the body, the piece 

 becomes smaller and the hole much larger than the original incision. 

 The opposite effect occurs when a toad is frightened. The skin of 



