350 COMMON REPTILES OF AN INDIAN GARDEN 



blade of a plantain leaf. The latter is tightly 

 stretched over the concavity of the shell, and the 

 snake, whilst securely held by the neck, is irritated 

 and encouraged to strike it. The result is that the 

 ends of the fangs penetrate the leaf and project 

 freely into the cavity beneath, so as to allow the 

 venom to drip into it. The quantity of venom that 

 a snake yields under such treatment varies greatly 

 in individual cases, according to the size and vigour 

 of the animal and the length of time that has 

 elapsed since a previous discharge took place. The 

 average weight of dry material yielded by a single 

 discharge of venom by cobras at Alipur was 0*254 

 gramme, and its average lethal value was on the 

 scale of 0*75 of a milligramme per 1 kilogramme of 

 body-weight in warm-blooded animals. In many 

 cases the amount was, however, much in excess of 

 the average, so that it is clear that a single efficient 

 bite may readily suffice to cause death even in the 

 case of very large animals, especially where the 

 lethal power of the venom is exceptionally high. 



The hamadryad, Naia bungarus, is practically 

 unknown as an inhabitant of the immediate neigh- 

 bourhood of Calcutta. The only well authenticated 

 instance of its occurrence within the area took place 

 many years ago in the Botanic Garden, and the 

 snake in this case may very probably have been 

 an imported one, conveyed by one of the native 

 boats that are constantly coming up the river from 



