62 THE ZOOLOGIST. 



recognition of these facts naturally leads the keepers to delay 

 changing the water as long as possible, particularly in the large 

 tanks, which take a very long time to get warm, and where 

 the Pythons, Boas, and Anacondas constantly bathe ; and it 

 becomes foul in consequence — probably the lesser of the two 

 evils, though doubtless both conditions have something to do 

 with the production of that serious disease of the mouth to 

 which I shall refer hereafter. The water should be changed 

 and the tanks cleansed frequently. 



The heat, as I have said, is best applied to the cage itself 

 rather than to the apartment in which it stands ; and there is 

 another reason for this, besides the one mentioned at the com- 

 mencement of this chapter. The very solidity of construction 

 which renders the den admirably calculated to keep in and 

 economise any warmth generated in its interior, serves often to 

 exclude that of the outer atmosphere. I have remarked this in 

 the Eeptilium of the Jardin des Plantes in Paris. The building 

 is heated by enormous stoves, and becomes at times quite 

 oppressive to the visitor. But tbe cages, which are glazed on 

 two sides and, in the case of the larger snakes, are so arranged 

 as to be visible from the outside of the house, have no special 

 appliance ; and one is quite surprised, standing in that sultry 

 air, to find on handling the reptiles how cold they are. As to 

 the mode of application, it is difficult to lay down any rules or 

 offer advice, since this must depend in every case upon the 

 situation and opportunities. Hot water is decidedly to be 

 preferred to hot air, and if a gas-stove is used it ought -to be 

 placed outside the building or in such a position that no vapour 

 may contaminate the air within the cage. Pipes should run 

 underneath the flooring in all directions, and at a very slight 

 depth from the surface (especially if it be composed of Portland 

 cement), as there will be a bed of gravel over this; it is advisable 

 also to have a pipe at the upper part of the cage, so that the 

 reptiles may have an inducement to leave the floor and take 

 plenty of exercise. This upper pipe had better be buried in the 

 wall or walls along which it passes ; if exposed, it must be very 

 carefully shielded with thick felt, so that no more than a warmth 

 comfortable to the hand can penetrate. A gentleman writes to 

 me from the north of Germany that he has improved upon this 

 detail, which I sent him when he was building a vivarium for 



