of Mammtferous Animals. 311 



guides them, the power which acts upon their organs, and which 

 directs and determines their motions. 



All the analogies founded upon the observation of animals in 

 a state of liberty made it in general be regarded as a certain 

 fact, that the intelligence of each animal in its development fol- 

 lowed the progression which we observe in the development of 

 the human intellect. Thus the animal, like man, was born with 

 intellectual faculties, of which the simple germ could only at 

 first be perceived ; in its youth these faculties shewed more vi- 

 vacity than strength, and they only arrived at their perfection 

 when they were matured by age. The study of animals in a 

 state of captivity has had the effect of destroying this prejudice ; 

 for it was necessary to compare them with themselves at differ- 

 ent periods of their life, and consequently to follow their de- 

 velopment, in order to perceive that the young are incomparably 

 more intelligent than those which have attained the age of matu- 

 rity. And all animals were not calculated for this sort of in- 

 quiry ; we could not reckon upon the species modified by domes- 

 tication ; those whose intellect is limited gave no sensible result ; 

 and the carnivora, constantly obliged to exercise all their facul- 

 ties, were in the same condition. It was necessary to have re- 

 course to the species which with respect to intellect have been 

 more favoured, and yet whose existence does not absolutely de- 

 pend upon the use which they make of it ; in a word, to the 

 monkeys, which live on fruits, a species of food always abound- 

 ing in the countries they inhabit, and which can never be 

 brought in a nearer relation to us than the state of captivity. 

 But this observation is not confined to the establishing of a new 

 and important fact ; it has, moreover, thrown light upon a ques- 

 tion of high interest. In observing that in their early youth 

 the intellectual faculties with which animals have been endowed 

 have acquired all the extent and activity of which they are ca- 

 pable, and that they begin to diminish as soon as the age of vi- 

 gour arrives, we have acquired a new demonstration of the fun- 

 damental difference which distinguishes them from man. Pre- 

 vious to this we could only, like several observers, have found 

 this difference through the analysis of their fortuitous actions, 

 in which the reflective faculty never manifests itself; now it 

 arises from the very phenomenon which we have been pointing 



