142 



LIFE. 



similar order, under a still more comprehen- 

 sive expression.* But it is not in every de- 

 partment of science that the same facility in 

 the attainment of general laws exists. Where 

 the phenomena are of such a complex nature 

 that the operation of the real cause is, as it 

 were, masked by the influence of concurrent 

 conditions, or where (as often happens in phy- 

 siology) the effects of the same apparent cause 

 are totally different according to the instru- 

 ments through which it operates, it is obvious 

 that there will be great difficulty in the first 

 stage of the inductive process that of the clas- 

 sification of phenomena, so great, indeed, 

 that it may be regarded as one of the principal 

 obstacles to the advancement of those branches 

 of science in which it presents itself. Of all 

 the branches of physical science, that of me- 

 teorology is the most obscure and apparently 

 uncertain, and bears most resemblance to phy- 

 siology. The changes which it concerns 

 are daily and hourly occurring under our 

 observation ; and the general laws which 

 govern them are tolerably well ascertained ; 

 yet the mode in which their actions are com- 

 bined is so peculiar, as hitherto to have baffled 

 the most persevering and penetrating enquirers, 

 in their attempts to explain or predict their 

 operation. But no one thence feels justified 

 in assuming the existence of any new or un- 

 known cause, capable of controlling or sub- 

 verting the influence of the rest ; and such a 

 proceeding would not be justifiable, until all 

 their possible modes of action have been ascer- 

 tained and put aside, leaving certain residual 

 phenomena not otherwise to be accounted for. 



The peculiar difficulties which beset the in- 

 vestigation of the laws of vital action have 

 greatly retarded our acquaintance with them, 

 and have even led to the belief that the induc- 

 tive process is not applicable to them. These 

 difficulties have arisen, in the first place, from 

 the obstacles in the way of the collection of 

 phenomena ; secondly, from the peculiarly com- 

 plex nature of these phenomena ; and, thirdly, 

 from the vague hypotheses which have pre- 

 vented them from being classed as simple facts 

 on which generalisations are to be erected, or 

 effects whose sources are to be ascertained, but 

 which have clothed them in the delusive aspect 

 of laws or causes. Until, therefore, the prin- 

 ciples of philosophical induction are thoroughly 

 understood, the peculiar combinations in which 

 vital phenomena present themselves to our 

 notice, their apparent dissimilarity from the 

 changes which we witness in the world around, 

 and their obvious adaptation to particular ends, 

 might lead us astray into the labyrinth of un- 

 profitable speculation with regard to the pre- 

 siding agencies by which they are governed ; 

 and the retrospective view which we shall pre- 

 sently take will afford many examples of this 

 error, even in recent times, and will in fact 

 show that the legitimate objects of investiga- 



* Such would seem to be the tendency of certain 

 recent speculations in regard to gravitation, mole- 

 cular and electrical attraction, and chemical affinity. 



tion, and the true mode of pursuing them, 

 are only now beginning to be understood. 



When we observe the circumstances under 

 which vital actions occur, we perceive that at 

 least two conditions are required for their pro- 

 duction. The first is a structure in that pecu- 

 liar state which is termed organised (see OR- 

 GANISATION); the second is a stimulus of 

 some kind fitted to act upon it. Now this is 

 no more than what we observe in the world 

 around, where every action involves two con- 

 ditions of a corresponding character. When 

 water is changed into steam, for example, it is 

 by the stimulus of heat. When a stone falls 

 to the ground, it is by the attraction which the 

 mass of the earth exercises over its own. The 

 difference consists in the peculiarity of the 

 actions exhibited by living beings, which are 

 not identical with those elsewhere presented to 

 us, and which we cannot imitate by any phy- 

 sical or chemical operations. Whilst the me- 

 chanical philosopher, then, refers to the pro- 

 perty of gravitation as the cause of the effect 

 just mentioned, the physiologist refers to the 

 capability of exhibiting vital actions, when 

 excited by certain stimuli, as the property of 

 the tissue which manifests them. Thus, when 

 he witnesses the contraction of a muscle, under 

 the stimulus of innervation or of galvanism, 

 Sec. he regards the effect as due to a property 

 of contractility inherent in the muscle, and 

 standing in precisely the same relation to its 

 organic structure, as gravity to matter in ge- 

 neral. So far, however, the advance in our in- 

 quiry is more apparent than real ; since it may 

 fairly be said that, to speak of contractility as 

 the character of a body exhibiting contractions, 

 is merely a change in words without absolute 

 gain. But, having done this, we are led to 

 inquire the conditions under which this con- 

 tractility operates ; and to analyse a number of 

 phenomena apparently dissimilar, so as to at- 

 tain the general law of its action. In this man- 

 ner we proceed in regard to other classes of 

 phenomena; and we shall thus acquire (when 

 our data are sufficiently precise and extensive) 

 a knowledge of the properties of all the tissues 

 or organised structures which compose the 

 living body, and of the phenomena which 

 their single or combined operation will pro- 

 duce, under the influence of their respective 

 stimuli. 



But the physiologist will not stop here. He 

 will seek to inquire to what these properties 

 are due, which are so different from anything 

 exhibited by the same matter before it had be- 

 come a part of the organised system. And, 

 if he consider the matter in all its bearings, 

 with a total dismissal of prejudice, he will be 

 unable, we think, to arrive at any other conclu- 

 sion than that they are due to the act of organi- 

 sation, which, in combining the inorganic ele- 

 ments into new compounds, and giving them 

 a peculiar structure, calls out or developes in 

 them properties which had previously existed 

 in a dormant state, but required these circum- 

 stances for their manifestation. To this ques- 

 tion, however, we shall presently return, when 



