32 DISEASE IN WILD MAMMALS AND BIRDS 
stances are without doubt most simply kept clean, but 
they are heat-conducting and remain cold or damp longer 
than wood or the ground. It may be claimed that the 
latter two cannot be disinfected so well, but this need not 
militate against their use. Wood can be disinfected by 
sunlight or by mechanical cleaning plus disinfectants, by 
a blast lamp and by paint. The ground will disinfect 
itself if allowed to lie fallow for a time, or it may be 
turned over after sprinkling with lime. It is fair to note 
that the New York Zoological Garden reduced their mor- 
tality, especially from verminous pneumonia, by changing 
some deer herds to concrete paved enclosures; if that 
were the only change made the result would be very 
significant, but it should not be forgotten that another 
clean ground range might have served as well to a herd 
from which the infected ones had died. My own observa- 
tions with guinea-pigs, rabbits, mice and dogs lead me to 
believe that they thrive and breed better on wooden floors 
than on metal or stone. 
I have tried to work out figures to show that more 
animals die when housed in enclosures of stone and metal 
than when upon the earth or on wood, but the attempt has 
been unsuccessful chiefly because of the presence of epi- 
demics and parasites, principally among the birds. The 
attempt was further embarrassed because some members 
of an order are housed on both floorings. However, there 
was no great advantage for the metal and concrete floors 
even after the epidemic had been discounted. This Gar- 
den does not have a great number of pneumonias, a 
disease said to be favored by dampness and cold, but 
those that occur are chiefly among the small mammals, on 
wooden floors and in the large bird house in cages of con- 
crete and metal. However, the construction of both these 
houses permits the visitors to approach very close to the 
cage, a factor that doubtless explains the dispropor- 
tionate incidence of inflammation of the lungs. In so far 
as outdoor fowl and ungulate ranges are concerned, they 
