ON INStlNC l . 



actions are the actions of the hving principle ^ and either is that po^er 

 which characteristically distinguishes organized from unorganized matter, 

 and pervades and regulates the former as gravitation pervades and regu- 

 lates the latter, uniformly operating by definite means, in definite cir- 

 cumstances, to the general welfare of the individual system or of its sepa- 

 rate organs ; advancing them to perfection, preserving them in it, or lay- 

 ing a foundation for their reproduction, as the nature of the case may re- 

 quire. It applies equally to plants and to animals, and to every part of the 

 plant as well as to every part of the animal, so long as such part continues 

 alive.* It is this which maintains from age to age, with so much nicety 

 and precision, the distinctive characters of different kinds and species ; 

 which, as is noticed in a preceding study, carries off the waste or worn 

 out matter, supplies it with new,t and in a thousand instances suggests the 

 mode of cure, or even effects the cure itself, in cases of injury or disease. 

 It is " the divinity that stirs within us" of Stahl ; the vis medicatrix naturae 

 of Hoffman and Cullen,| and the physicians of our own day. It is hence 

 the strawberry travels from spot to spot, and the cod or the cuckoo, with 

 a wider range, from shore to shore, or from climate to climate. § 



In supplying the place of reason, it is perpetually assuming its sem- 

 blance. Let us take an example or two from both the vegetable and the 

 animal world. 



In order that the seeds of plants should produce and perfect their respec- 

 tive kinds, it is necessary that their shoots should rise to the surface of the 

 earth to enjoy the benefit of light and air. Now in whatever direction 

 the eye of a seed, from which germination first radiates, is placed, these 

 shoots ascend equally to the surface, either in curved or straight lines, 

 according as such ascent may be most easily accomplished. Mr. John 

 Hunter sowed a quantity of peas and beans with their eyes placed in dif- 

 ferent directions, in a tub, which he afterwards inverted, so that the bottom 

 was turned uppermost, while the mould was prevented from falling out by 

 a fine net. And in order that the under surface might possess a superior 

 stimulus of light and heat to the upper, he placed looking glasses around 

 the mouth of the tub in such a way that a much stronger light was re- 

 flected upon the inverted mould than that of the direct rays of the sun ; 

 while at the same time, he covered the bottom of the tub with straw and 

 mats to prevent the mould, in this direction, from being affected by 

 solar influence. Yet the same instinctive law of ascent still prevailed. 

 After waiting a considerable length of time, and perceiving that no shoots 

 had protruded through the lower surface of the mould, he examined the 

 contents of the tub, and found that they had all equally pressed upwards 

 and were making their way through the long column of mould above them, 



* Mr. Knight, while he seems desirous of resolving the principle of. vegetable action into 

 centripetal force, has shown that the sap of plants, as it exists in the leaves of potatoes and 

 mint, and the leaves and shoots oi the vine, possess what he calls organizable matter ; and 

 when plunged in a moist and warm soil will produce bulbs or roots more or less perfect, or 

 at least preserve and endeavour to extend life. — Phil Trans. 1816, p 289. The whole, like 

 the reproduction of polypes and worms from sections, ought rather to be resolved into the 

 common law of instinct, the aim of which is health, preservation, or reproduction ; and 

 hence the sap of plants seems as much alive as the blood of animals. 



T Ser. I. Lect. XIV. 



t First lines, vol. i. p. 91. 105. 



§ In conformity with the general principles of his system. Dr. Darwin ascribes this extra- 

 ordinary faculty also to the power of reason. " It is probable," says he, " that emigrations 

 were at first undertaken as accident directed, by the more adventurous of their species, and 

 learned from one another Mice the discoi'ieries of mankind in navigation." — Zoon. ecci 



