328 ON MATERIALISM 



any thing else; all which, again, so far as we are acquainted with them, arc 

 nothing but matter in different states of modification. Yet the animal egg 

 produces a new and a much higher power, which we denominate sensation, 

 while the vegetable egg produces nothing of the kind. What is sensation, 

 and from what quarter has it been derived ? Is it a mere property, or a dis- 

 tinct essence ? Is it material, or is it immaterial 1 



This, also, has occasionally been called instinct, and been contemplated as 

 of instinctive energy. With equal confusion it has also been called or con- 

 templated as a property of mind. It is neither the one nor the other : it is 

 equally different from both. We trace, indeed, its immediate seat of resi- 

 dence ; for we behold in the silk-worm a peculiar organ which does not exist 

 in the mustard-plant, and to which, and which alone, sensation always at- 

 taches itself; and to this organ we give the name of a nervous system. But 

 to become acquainted with the organ in which sensation resides is no more 

 to become acquainted with the essence of sensation itself, than to know the 

 principal of life because we know the general figure of the individual animal 

 or vegetable in which it inheres ; or than to know what gravitation is because 

 we see the matter which it actuates. 



As simple nerves, or a nervous chord, such as that of the spinal marrow, is 

 the proper organ of sensation or feeling, the gland of a brain, from which 

 the nervous chord usually, though not always, shoots, is the proper organ of 

 intelligence ; and as I had occasion to observe in a former study, when 

 lecturing upon the subject of the senses, the degree of intelligence appears, 

 in every instance we are acquainted with, to be proportioned, not, indeed, to 

 the size of the brain as compared with that of the animal to which it belongs, 

 as was conjectured by Aristotle, and has been the general belief almost to the 

 present day, but as compared with the aggregate bulk of nerves that issue 

 from it.* The larger the brain and the less the nerves, the higher and more 

 comprehensive the intelligence: the smaller the brain and the larger the 

 nerves, the duller and more contracted. In man, of all animals whatever, 

 the brain is the largest, and the nerves, comparatively with its bulk, the 

 smallest : in the monkey tribes it makes an approach to this proportion, but 

 there is still a considerable difference ; in birds a somewhat greater differ- 

 ence ; in amphibials the brain is very small in proportion to the size of the 

 nervous chord ; in fishes it is a bulb not much larger than the nervous chord 

 itself; in insects there is no proper brain whatever; the nervous chord that 

 runs down the back originating near the mouth ; sometimes of a uniform 

 diameter with the chord itself, and sometimes rather larger; and in infusory 

 and zoophytic worms we have no trace either of nerves or brain. 



In these last, therefore, it is possible, and indeed probable, as I have already 

 observed, that there is no sensation : the vital principle, and the instinctive 

 faculty, which is the operation of the vital principle, by the exercise of cer- 

 tain natural powers constantly appertaining to such principle, alone produc- 

 ing all the phenomena of life, as in plants. In most insects, for the same 

 reason, it is possible, and indeed probable, that though there is sensation, 

 there is little or no intelligence : the brain, which is the sole seat or organ of 

 intelligence, being totally destitute, in most of them, and of very minute com- 

 pass in the rest. In fishes we have reason to apprehend different degrees of 

 intelligence: in many amphibials somewhat more; more still in birds and 

 quadrupeds, and most of all in man. 



But what is intelligence, which is a distinct principle from sensation, and 

 to which, as in the case of sensation, a distinct organ is appropriated ? An 

 organ, moreover, which, like that of simple sensation, may be also produced 

 out of an insentient egg by the mere application, so far as we are able to trace 

 the different substances in nature, of a certain proportion of heat ; for the egg 

 of' the hen, unquestionably insentient when first laid, becomes equally 

 hatched and endowed with the organs and properties both of sensation and 

 intelligence, by the application of a certain portion of warmth, whether that 



* Ser. i. Led. xv. 



