44 The Diseases of Animals 
the rabbits from burrowing out, the walls must be ear- 
ried down deep into the earth, or else the floor of the 
yards must be paved or covered with chicken- wire. 
Fig. 18. Belgian hares 
Rabbits are fond of burrowing, and it is therefore 
generally considered beneficial to have the floors of dry 
earth. If the pens are kept well littered with straw or 
similar material, the animals seldom dig much, but if 
they once get access to the earth they will burrow rapidly. 
