372 FUNCTIONS OF THE NERVOUS SYSTEM. 



ception or notion of the object becomes inseparably connected with the sen- 

 sation ; and thus it is excited by the latter, without any knowledge on the 

 part of the individual, that a mental operation has taken place. 



490. Such Perceptions are termed acquired, in contradistinction to the in- 

 tuitive perceptions, of which the lower animals seem to possess a large num- 

 ber. The idea of the distance of an object, for example, is one derived in 

 Man from many sources, and is the result of a long experience ; the infant, 

 or the adult seeing for the first time, has to bring the senses of sight and of 

 touch to bear upon one another, in order to obtain it ; but, when once the 

 power of determining it is acquired, the steps of the process are lost sight of. 

 In the lower tribes of animals, however, in which the young receive no assist- 

 ance from their parents, there is an evident necessity for some immediate 

 power of forming this determination ; since they would not be able to obtain 

 their food without it. Accordingly, they manifest in their actions a percep- 

 tion or governing idea of distances, which can only be gained by Man after 

 long experience. A fly-catcher, for instance, just come out of its shell, has 

 been seen to peck at an insect, with an aim as perfect as if it had been all its 

 life engaged in learning the art. In some cases, animals seem to learn that 

 by intuitive perception, at which Man could only arrive by the most refined 

 processes of reasoning, or by the. careful application of the most varied expe- 

 rience. Thus, a little fish, named the Chsetodon rostratus, is in the habit of 

 ejecting from its prolonged snout, drops of fluid, which strike insects that hap- 

 pen to be near the surface of the water, and causes them to fall into it, so as 

 to come within its own reach. Now, by the laws of refraction of light, the 

 place of the Insect in the air, will not really be that at which it appears to 

 the Fish in the water ; but it will be a little below its apparent place, and to 

 this point the aim must be directed. But the difference between the real and 

 the apparent place will not be constant ; for the more perpendicularly the rays 

 enter the water, the less will be the variation; and, on the other hand, the 

 more oblique the direction, the greater will be the difference. Now it is im- 

 possible to imagine but that, by an intuitive perception, the real place of the 

 Insect is known to the Fish in every instance, as perfectly as it could be to 

 the most sagacious Human mathematician, or to a clever marksman, who had 

 learned the requisite allowance in each case by a long experience. 



490*. In Man, the acquirement of perceptions is clearly a Cerebral opera- 

 tion ; but their intuitional formation in the lower animals is probably to be 

 regarded as one of those processes to which the Sensory ganglia are subserv- 

 ient. The same may be said of many of the intuitive perceptions in Man ; 

 which, if analyzed, are found to be connected rather with the instinctive and 

 emotional tendencies, than with the intellectual powers ; the perceptions 

 which minister to the exercise of these last, being the result of experience. 

 Thus, it has been well remarked by Dr. Alison, that the changes which Emo- 

 tions occasion in the countenance, gestures, &c., of one individual, are instinc- 

 tively interpreted by others ; for these signs of mental affection are very early 

 understood by young children, sooner than any associations can be supposed 

 to have been formed, by experience, of their connection with particular modes 

 of conduct; and they affect us more quickly and strongly, and with nicer 

 varieties of feeling, than when it is attempted to convey the same feelings in 

 words, which are signs addressed to the intellect. 



491. By a certain retentive power, which appears to be peculiar to the 

 Cerebrum, Sensations and the simple ideas or Perceptions they excite, are 

 stored up (so to speak) in such a manner, as to become the subjects of further 

 mental operations at a time more or less remote. They then present them- 

 selves as renewed images of past sensations ; and these may recur, either 

 involuntarily, or by a special direction of the mind towards them by an effort 



