170 THE SPEECH OF MONKEYS. 



these sounds when alone or as a mere pastime, 

 but only at such times as some one is present to 

 hear them, either some person or another mon- 

 key. They understand the sounds made by other 

 monkeys of their own kind, and usually respond 

 to them with a like sound. They understand 

 these sounds when imitated by a human being, 

 by a whistle, a phonograph, or other mechanical 

 devices, and this indicates that they are guided 

 by the sounds alone, and not by any signs, gest- 

 ures, or psychic influence. The same sound is 

 interpreted to mean the same thing and obeyed 

 in the same manner by different monkeys of 

 the same species. Different sounds are accom- 

 panied by different gestures, and produce differ- 

 ent results under the same conditions. They 

 make their sounds with the vocal organs and 

 modulate them with the teeth, tongue, and lips, 

 in the same manner that man controls his vocal 

 sounds. The fundamental sounds appear to be 

 pure vowels, but faint traces of consonants are 

 found in many words, especially those of low 

 pitch, and since I have been able to develop cer- 

 tain consonant sounds from a vowel basis, the 

 conclusion forces itself upon me that the conso- 

 nant elements of human speech are developed 



