288 BEASTS AND MEN. 
_ But it is more than ever necessary in the case of such highly 
_ organised animals as anthropoid apes. When they are con- 
stantly playing about together, with plenty of stimulus to keep 
them always on the move, their digestion is kept in good 
order, their appetite maintained, and a high tone. preserved 
throughout the system. They are especially subject .to psy- 
chical influences ; and, the more they are kept in. contact with 
human beings, the more likely are they. to thrive and. forget 
their captivity. 
I feel pretty confident that it is mental depression, and 
not any physical ailment, which makes it so difficult to: keep 
gorillas for any length of time in captivity. . None of those 
which have come to me have ever survived for long their 
arrival i in Europe. They show every day a gradually dim- 
inishing interest in their surroundings, until at last they. refuse 
food altogether and are found dead one morning in their cage 
It is true that there have been instances now and again of 
gorillas being kept for a considerable period in captivity, but 
such cases are only exceptions. Perhaps in the course of 
time I shall succeed in discovering the proper method of 
treating these great apes. At present I have learnt little 
of them except the conviction that their trouble is psychical 
and not physical. It has hitherto been the almost universal 
habit to credit gorillas, and for the matter of that chimpanzees 
and orangs too, with much less intensity: of feeling than they 
actually possess. 
Their memories at least ‘are undeniably excellent. After 
the two orangs had been in my. possession for. a period: ‘of 
twelve months, their former owner came to’ the park to see 
them... They instantly recognised him and showed their 
pleasure in the most unmistakable manner. Qne may. ob- 
serve in these creatures the. origin of the capacity: for laughter. 
When they are amused the corners of. the mouth move out- 
wards, showing the teeth between. their lips. . In Moritz 
particularly, the play of the expressions on the countenance 
is very noticeable. The ‘keeper can tell at a glance, 
