TWENTIETH ANNUAL REPORT Sil 
PURIFICATION OF AIR IN BUILDINGS AT PARK. 
In an attempt to purify the foul air and eradicate animal 
odors in the different buildings at the Park, your committee 
authorized the installation of ozone machines. These machines 
are operated by electricity and the consumption of current is 
about the same as for one electric light bulb. The results have 
been most gratifying. Nine machines have been installed 
during 1915, at a cost of $75 each, chargeable against the Main- 
tenance Fund. 
MEDICAL DEPARTMENT. 
The general health of the mammals has remained good 
throughout the year, the deaths occurring principally among 
the small mammals and South American monkeys. 
Except where an immediate autopsy was necessary to deter- 
mine the cause of death in order to safeguard our collections, 
all animals have been turned over to the Prosector’s Department. 
It has been necessary to destroy an increasing number of ani- 
mals from our original stock on account of old age. During 
the coming year it will be necessary to destroy a number of 
animals whose usefulness as exhibition specimens is past, owing 
to general debility resulting from old age. Many of these 
animals were of adult age when received at the Park, and have 
been on exhibition continuously for more than a dozen years. 
With some of these animals, especially where the specimen is 
rare, and difficult or impossible to replace, it is often difficult 
to decide just when it has reached such a state of debility as 
to justify its merciful destruction. 
The new Animal Hospital which has been greatly needed 
for many years is now nearly completed, and should be ready 
for service about March, 1916. This building will provide excel- 
lent facilities for the isolation and treatment of medical and 
surgical cases, and at the same time by the prompt removal 
of suspicious cases of illness, reduce the danger to the healthy 
animals from infectious diseases. 
FORESTRY DEPARTMENT. 
The usual amount of general maintenance work, such as 
cleaning of walks, lawns and buildings, the collection and dis- 
posal of garbage, refuse, manure and ashes, the general upkeep 
