poison of the common toad. 129 



them ; 1 have detected it in a notable quantity in the bile, in 

 a minute quantity in the viscid fluid lubricating the tongue, 

 and also in the urine, and even in the blood. 



Reflecting on the use w^hich this fluid may.be of to the 

 toad, it has occurred to me that it may answer two purposes, 

 and these of importance to this abhorred but innocent 

 reptile. 



As the external surface of the skin is smeared with this 

 " sweltered venom '' (the very appropriate epithet given it 

 by our great dramatic poet), it must serve to defend it 

 against the attacks of carnivorous animals : " a toad to eat " 

 is a proverbial expression well known ; and the facts adduced 

 show its propriety and force. I may here add, that nature 

 has given this animal an additional security against attack, in 

 providing it with integuments of great thickness, and strength, 

 and hardness ; which last-mentioned quality is imparted by 

 a layer of cutis almost analogous to bone, immediately under 

 the rete mucosum, abounding in phosphate and carbonate of 

 lime, and carbonate of magnesia, semi-transparent, and yet 

 so firm that it is not easily cut. 



As the fluid contains a substance which is very inflamma- 

 ble, and as it may be considered excrementitious, though the 

 blood is very slightly impregnated with it, it may serve to 

 separate a portion of carbon from the blood ; and thus in its 

 formation be auxiliary to the function of the lungs. In sup- 

 port of this idea, I may remark, that I find the pulmonary 

 arteries of the toad are each divided into two branches, one 

 of which goes to its respective lung, and the other, very 

 little smaller, to the cutis, between the head and shoulder, 

 on each side, and is extensively ramified where the largest 



MDCCCXXVI. S 



