30 INTRODUCTION. 



IV. Dermal Secretion. 



The skin of the dorsal surface of all Batrachians is, 

 as we have seen, studded with glands and follicles. 

 In various species, of which our Bvfones are good 

 examples, some of the larger glands appear as very 

 prominent warts pierced with wide pores, especially a 

 large mass situated on each side of the back of the 

 head behind the eyes, which has received the mis- 

 nomer of parotid, a name now generally changed to 

 parotoid gland. These glands secrete, more or less 

 abundantly according to the species, a viscid or milky 

 more or less and variously odorous fluid, which is 

 exuded, when the animal is disturbed, by means of the 

 contraction of small muscles disposed in the skin 

 around the glands. If the larger glands be pressed 

 or subjected to an electric current the secretion is 

 squirted out with great force, and sometimes to a 

 considerable distance. Kobert recommends, as the 

 best means of obtaining an abundant supply of toad- 

 2:)oison, the subcutaneous injection of a small dose of 

 chloride of barium ; after a few minutes the animal is 

 so covered with its secretion as to appear as if coated 

 with whitewash. The object of the secretion is to 

 guard Batrachians from the attacks of various enemies. 

 A dog will not often repeat the experiment of seizing 

 a toad; the signs of pain which it evinces after the 

 poisonous fluid has come into contact witb its mouth 

 is familiar to most of those who have kept young 

 dogs in the country. That excellent Hungarian 

 naturalist. Prof. v. Mchcly, relates the serious effects 

 of the poison of Biifo viridis on a small terrier which 

 accompanied him on a collecting excursion. A large 

 toad, found under a stone, was at once attacked by 

 the dog, but no sooner seized was let go again with 

 signs of great repulsion ; the toad had instantly become 

 covered with a thick white secretion. The dog a,p- 

 2;)roached it'oncemore and then withdrew, sneezing and 



