160 ZOOLOGY. 



other animals acquire their knowledge, there remains the 

 study of the power which determines their actions and the 

 phenomena of the understanding. This hranch of physiology 

 having been more cultivated by philosophers than naturalists, 

 we shall confine our remarks thereon to a brief space. 



It is man alone who possesses the faculties we allude to in 

 a high order, and it is man who naturally has been most 

 observed in this respect; our comparisons have reference 

 constantly to man ; by him we judge of other animals. 



307. Faculties of the Human Understanding. Im- 

 pressions made on the external senses by the external world 

 are transmitted to the brain by the nerves : they are then 

 called sensations. Sensation, then, is quite distinct from an 

 impression ; it is an impression perceived ; it implies con- 

 sciousness ; what is not perceived has no existence, for us. 

 The perceiving faculty is usually spoken of as the mind, the 

 spirit (esprit), the soul ; the thinking, perceiving, and reflect- 

 ing power, conscious of its own independent existence. 



308. Over this consciousness we have no power during 

 sleep, but when awake we can direct it to one object to the 

 exclusion of others. When thus forcibly and strongly called 

 on by one impression, pain ceases to be felt, and the external 

 world is no longer observed. This faculty is called the power 

 of attention, which varies almost in every individual. 



309. The constant relation of certain sensations to cer- 

 tain impressions leads to the inference that the one causes 

 the other ; that the one is the effect, the other the cause. We 

 arrive at this conclusion by the natural powers of induction. 

 We thus acquire a knowledge of the external world, and we 

 learn to judge by comparison of the different qualities of 

 objects. 



Soon the mind does not stop at this point, but proceeds to 

 weigh more and more carefully the impressions and sensations 

 thus received; the faculty of judging and, (comparing becomes 

 rapid and surer ; it is not the senses which are exercised, it 

 is the judgment ; the organs of sense require no education. 

 And here man's faculties would stop, were it not for another 

 faculty, by which sensations long since received can be re- 

 called, and compared with each other and with those then and 

 there present. 



310. This faculty is the memory ; by its means we 

 recal the sensations, more or less vividly, more or less ac- 

 curately, according to our natural powers of perception. The 



