Ig6 DR ALISON'S OBSERVATIONS ON 



action, the cases in which it acts, and those in which it is unconcerned, are to a 

 certain degree defined ; — and that a short and general illustration of these points 

 may be of some advantage, if not to the progress of the science, at least to the 

 due appreciation, and proper generalization and expression of the knowledge 

 whicli has been already acquked. 



To shew the importance of this inquiry, I need do no more than quote a 

 single sentence from Cuvier, with a statement which is nearly a commentary 

 upon it by Professor Whewell. " It belongs to modern times to form a just 

 classification of the vital phenomena ; and upon the zeal and activity given to 

 the task of analysing the forces which belong to each organic element, depends, 

 according to my judgment, the advancement of physiology."* " As the vital 

 functions became better understood, it was seen more and more clearly at what 

 precise points of the process it was necessary to assume a peculiar vital energy, 

 and what sort of properties this energy must be conceived to possess. It was 

 perceived when, and in what manner and degree, mechanical and chemical 

 agencies were modified, oveiTuled, or counteracted by agencies whicli must be hy- 

 per-inechanical and kt/j)er-chemtcal." " In attempts to obtain clear and scientific 

 ideas of the vital forces, we have first to seek to understand the cause of change 

 and motion in each function, so as to see at what points of the process peculiar 

 causes come into play ; and next, to endeavour to obtain some insight into the 

 peculiar character and attributes of these causes.^'-^ 



When we say that the chemical changes which take place in living bodies 

 are elucidated, we mean, of com-se, that they are referred to general laws, by 

 which the phenomena observed in this department of Nature are found, by expe- 

 rience, to be regulated. And when we say that these are laws of vitality or of 

 vital action, we mean merely, that they are laws deduced fi'om the observation 

 of phenomena peculiar to the state of life, — taking for granted that it is always 

 possible to describe, and practically to distinguish, those substances which we caU 

 living, from inorganic or dead matter ; and that the only correct definition of 

 vital principles or vital powers, is, that they are the laws or the powers which 

 regulate the phenomena that are peculiar to the state of life. They are the gene- 

 ral expression of the results of the observation, and generaUzation of the facts, 

 which are observed in this department of nature, and which are ascertained to 

 belong to this department alone. 



We are not, indeed, justified in asserting the existence of laws peculiar to 

 the state of life, merely by the negative observation, that the phenomena refeired 

 to them are inexplicable by any known laws of inorganic or dead matter ; we must 

 have the positive observation that they are inconsistent with — that they take place 



* Hist, des Sciences Naturelles depuis 1789, p. 218. 



t Philosophy of the Inductive Sciences, vol. ii., pp. 39 and 47. 



