THE GORILLA 241 



reflections, I doubt whether this sound is made by the 

 gorilla. There are reasons to believe that it is made by 

 the chimpanzee. 



I observed that my own chimpanzees made a sound 

 exactly the same as that I heard in the forest, except that 

 it was less in volume. This was due to the age of the 

 apes that made it. I could induce them at any time to 

 make the sound, and frequently did so in order to study it. 

 After my arrival in New York I found that Chico — the 

 big chimpanzee belonging to Mr. Bailey — frequently made 

 the same sound. This he always did at night. The cry 

 was said to be so loud and piercing that it fairly shook the 

 stately walls of Madison Square Garden. From reading 

 the description given by the late Professor Romanes of 

 the sound made by " Sally " in the London Gardens, it 

 appears that she made the same sound. It is well known 

 to the natives that chimpanzees beat on some sonorous 

 body, which the natives call a drum. In 1890 I called 

 attention to the beating practiced by the two chimpanzees 

 in the Cincinnati Gardens. They frequently indulged in 

 beating with their knuckles upon the floor of their cage. 

 This was done chiefly by the male. The late E. J. Glave 

 described to me the same thing as being done by the 

 chimpanzees in the middle Congo basin. 



It is not probable that two animals of different genera 

 utter the same exact sound, and this is more especially true 

 of a sound that is complex or prolonged. Neither is it 

 likely that the two would have a common habit, such as 

 beating on any sonorous body. Since it is certain that one 

 of these apes does make the sound described, it is more 



