PREFACE 



XI 



his having never made a mistake, but rather on his readiness to admit that 

 he has done so, whenever the contrary evidence is cogent enough. 



In the present book I venture to lay down no expression of opinion as to 

 the problem of "Vitalism," although it is scarcely possible to hide my feelings 

 on the matter. I take it that there is no serious difficulty as to the kind of 

 phenomena to be classed as "vital," and no dispute as to what are the 

 problems with which the physiologist has to deal. If asked to define " life," 

 I should be inclined to do as Poinsot, the mathematician, did, as related by 

 Claude Bernard (1879, p. 23), " If anyone asked me to define time, I should 

 reply : ' Do you know what it is that you speak of ? ' If he said ' Yes,' I 

 should say, ' Very well, let us talk about it.' If he said ' No,' I should answer, 

 ' Very well, let us talk about something else.' " The great physiologist, in 

 another place (1878, pp. 116-117), describes what seems to me to be the most 

 profitable attitude to take with regard to the question of vitalism ; he says, 

 " There is in reality only one general physics, only one chemistry, and only 

 one mechanics, in which all the phenomenal manifestations of nature are 

 included, both those of living bodies as well as those of inanimate ones. In 

 a word, all the phenomena which make their appearance in a living being 

 obey the same laws as those outside of it. So that one may say that all the 

 manifestations of life are composed of phenomena borrowed from the outer 

 cosmic world, so far as their nature is concerned, possessing, however, a 

 special morphology, in the sense that they are manifested under characteristic 

 forms and by the aid of special physiological instruments." It must be 

 remembered, of course, that the special systems referred to are not to be 

 understood as outside the laws of physics and chemistry. All that we are 

 justified in stating is that, up to the present, no physico-chemical system has 

 been met with having the same properties as those known as vital ; in other 

 words, none have, as yet, been prepared of similar complexity and internal 

 co-ordination. A further point, with regard to which Claude Bernard's 

 attitude is far more inspiring than that of those who regard living things as 

 in perpetual conflict with external nature, may also be given in a translation 

 of his own words (1879, p. 67): "It is not by struggling against cosmic 

 conditions that the organism develops and maintains its place ; on the con- 

 trary, it is by an adaptation to, an agreement with, these conditions. So, the 

 living being does not form an exception to the great natural harmony which 

 makes things adapt themselves to one another ; it breaks no concord ; it is 

 neither in contradiction to nor struggling against general cosmic forces ; far 

 from that, it forms a member of the universal concert of things, and the life 

 of the animal, for example, is only a fragment of the total life of the 

 universe." (See also Kropotkin's attractive book, " Mutual Aid.") 



My object, then, is to discuss the physical and chemical processes which 

 intervene in these phenomena, so far as they are known. It must be kept 

 in mind that all the methods available for the study of vital processes 

 are physical or chemical, so that, even if there were a form of 

 energy peculiar to living things, we could take no account of it, except 

 when converted into known forms of chemical or physical energy 

 in equivalent amount. This fact was clearly insisted upon by 

 Burdon-Sanderson (1911, p. 164). Where explanation on these lines fails 

 as yet, I have usually been content to summarise the general laws of the 



