INSTINCT, SENSATION, AND INTELLIGENCE. 221 



quently, different effects. Instinct evinces an equal diversity in all these in- 

 stances. Gravitation'belongs equally to the smallest and to the largest por- 

 tions of unorganized matter: instinct, in like manner, belongs equally to the 

 smallest and to the largest portions of organized matter; it exists alike in 

 solids and in fluids ; in the whole frame and in every part of the frame; in every 

 organ, and in everv part of every organ, so long as the principle of life con- 

 tinues. Sir Isaac "Newton established the doctrine of gravitation, and over- 

 came all objections to it chiefly by the modesty with which he propounded 

 and illustrated it. Without inquiring into the nature of its essence, he con- 

 tented himself with recognising it by its operations and laws. It is the aim 

 of the present study to follow this great example ; and leaving all discussions 

 concerning the essence of instinct or of organized life, on which instinct is 

 dependent, and which constitutes its sphere, as matter constitutes the sphere 

 of gravitation, to point out nothing more than the nature of its action, and oc- 

 casionally to catch a glance at the laws by which it is regulated. 



From what has been already said, we see clearly that the power of instinct 

 runs equally through the limits of vegetable and animal life, and conse- 

 quently, that instinct, sensation and perception, whatever they consist in, are 

 powers or principles essentially different. Instinct is the common property 

 of organized life in all its forms, but life itself is not necessarily connected 

 either with reason or sensation ; and it is of no small consequence that we 

 attend to this curious and extraordinary fact, the proofs of which are abun- 

 dantly in our own possession. The blood is alive, and has all the common 

 properties of life, as was very satisfactorily shown in an antecedent lecture, 

 from the experiments of Mr. John Hunter; but we all know that it possesses 

 neither feeling nor intelligence: the bones, the cartilages, the cellular mem- 

 brane, and the cuticle are alive; but, in a state of health, they are equally des- 

 titute of both these properties, and whether in health or disease, are always 

 destitute of the latter. 



Sensation and perception, so far as we are capable of witnessing, can only 

 exist in appropriate organs, as nerves, or modifications of nerves, which are 

 the only known seat of the one, and the brain, .or some modification of brain, 

 which is the only known seat of the other. In the higher classes of animals, 

 as mammals, birds, amphibials, and fishes, the nerves take their rise from the 

 brain, or rather from some particular part of it. But this is not an indis- 

 pensable law of life; for, in insects, we meet with nerves, but no brain; and 

 in most zoophytic and many other tribes of worms, with neither brain nor 

 nerves. And hence, wherever these organs or either of them are discover- 

 able, it is consistent with right reason to infer, that the faculty also exists to 

 which they respectively give rise. But, on the contrary, where neither of 

 these organs exists, as in plants, and a multitude of the lowest tribes of ani- 

 mals, which in the zoological system of Lamarck are on this account denomi- 

 nated apathic or insentient,* we have the same reason for inferring that, 

 though life is present, and, indeed, in many instances, peculiarly tenacious 

 and vigorous, there is neither intelligence nor sensation ; and that the whole 

 of the vital functions and operations are performed, like the semblaaces of 

 intelligence in the preceding case, by the common law of instinct; which, 

 operating in different ways, in different organs, and beings of different struc- 

 tures, appertains to living-matter of every kind. 



These observations will apply to the vegetable as well as to the animal 

 kingdom; for plants have a close analogy to the senseless tribes, the tubi- 

 pores, madrepores, sponges, and infusory worms, we are now contemplating 

 in their structure and origin, as well as in the limited range of their powers; 

 these animals being in many instances equally simple in their make, and 

 equally destitute of locomotion, and equally propagating their kinds by the 

 generation of buds or bulbs, instead of by that of seeds or eggs. Like these 

 low kinds of animals, plants, moreover, are altogether without organs either 

 of sense or intelligence; and it is consequently correct to infer, that they are 



Philosophic Zoologique. 



