FACULTIES OF THE MIND. 277 



in the case of herbivorous animals, there are very marked 

 differences in the species of the same genus, as between the 

 ox and the buffalo, the horse and the zebra. 



IV. ON THE MUTUAL COMMUNICATION OF FEELING. 



It is necessary, for the exercise of the various intellec- 

 tual, but especially of the active powers, that animals should 

 be able to make known to others, the impressions which 

 they receive, or the propensities which they feel. In this 

 kind of mutual communication, there are various ways in 

 which the object is accomplished. The ear is subservient 

 to the purpose in some cases, the eye, and even the touch, 

 in others. The method of holding intercourse by means of 

 sounds, being the most general, first merits our attention. 



a. The communication of Feeling by means of Sounds 

 addressed to the Ear. Among animals which employ 

 sounds as the medium of expressing their thoughts, those 

 only possess what is termed a voice, which breathe by means 

 of lungs. The voice is generated, by the air expelled 

 from the lungs passing through the wind-pipe and mouth, 

 and exciting those vibrations in these parts which produce 

 sound. The variety of structure exhibited by the wind- 

 pipe and mouth, on which the different conditions of the 

 sounds depend, will afterwards come under our more par- 

 ticular examination. We are at present considering the 

 voice as an auxiliary power of the mind. Regarded in this 

 light, the sounds which are uttered in the communication of 

 feeling, are either natural or acquired. 



Every animal possessed of a voice, has the power of 

 emitting those sounds which may be termed its Natural 

 Language. These sounds, immediately after birth, are 

 exclusively occupied in expressing the presence of pain, or 

 the conditions of the instincts of food and temperature. 



