286 PHILOSOPHY OF ZOOLOGY. 
two kinds of letters are conjomed to form a word, the same 
changeableness of character in the vowels may likewise be 
perceived, But in attending to the language of different 
nations, more remarkable differences than these to which 
we have now alluded appear to exist. We may detect the 
same sound of vowels and ccnsonants, but these sounds 
are the symbols of other objects, and express different ideas. 
What, then, are those causes which operate in the produc- 
tion of such diversity of speech in the same species ? The 
following sources of change appear to include all the cir- 
cumstances which exercise any remarkable influence,—the 
structure of the organs,—the variety of situation, and the 
progress of civilization. 
When we consider the complicated structure of those or- 
gans destined to produce voice, the varied movements they 
execute in articulating the different sounds, added to the 
influence exercised by age, sex, constitution and habit on 
the various muscles, we may perhaps be disposed to con- 
clude, that we have discovered causes adequate to account 
for all the phenomena. It cannot indeed be denied, that 
these circumstances operate in the production of that pecu- 
liar mode of speaking, by which an mdividual may be dis- 
unguished from all his acquaintance. It may even be 
granted, that the sounds produced by one individual, and 
which were at first specific, may, by being imitated by 
the young, become general in the district. Differences 
may therefore arise in the manner of pronouncing the 
vowels, and perhaps one or two of the consonants, in 
the mode of accenting the syllables, and in the tone and 
energy of expression. A difference of organization, there- 
fore, may account for the existence of provincial sounds 
or dialects, but it offers no explanation of the fact, that 
the same syllables among different tribes do not express 
the same ideas nor appear in words in the same re- 
lative position, But as a proof that other causes operate 
