LIFE: ITS NATUEE, OEIGIN AND MAINTENANCE 9 



can only be described by the same term amoeboid, yet obviously pro- 

 duced as the result of purely physical and chemical reactions causing 



changes in surface tension of the fluids under exami- 



Similarity of move- na fcjon.* It is therefore certain that such movements 



ments in living and 



non-living matter. are not specifically 'vital,' that their presence does 



not necessarily denote ' life.' And when we investi- 

 gate closely even such active movements as those of a vibratile cilium 

 or a phenomenon so intimately identified with life as the contraction 

 of a muscle, we find that these present so many analogies with amoeboid 

 movements as to render it certain that they are fundamentally of the 

 same character and produced in much the same manner. f Nor can we 

 for a moment doubt that the complex actions which are characteristic 

 of the more highly differentiated organisms have been developed in the 

 course of evolution from the simple movements characterising the activity 

 of undifferentiated protoplasm ; movements which can themselves, as we 

 have seen, be perfectly imitated by non-living material. The chain of 

 evidence regarding this particular manifestation of life movement is 

 complete. Whether exhibited as the amoeboid movement of the proteus 

 animalcule or of the white corpuscle of our blood ; as the ciliary motion 

 of the infusorian or of the ciliated cell ; as the contraction of a muscle 

 under the governance of the will, or as the throbbing of the human heart 

 responsive to every emotion of the mind, we cannot but conclude that it 

 is alike subject to and produced in conformity with the general laws of 

 matter, by agencies resembling those which cause movements in lifeless 

 material.]: 



It will perhaps be contended that the resemblances between the 

 movements of living and non-living matter may be only superficial, 



and that the conclusion regarding their identity to 

 Assimilation and , . , , -, . , -,. . -. -, -, 



disassimilation. which we are led will be dissipated when we endeavour 



to penetrate more deeply into the working of living 

 substance. For can we not recognise along with the possession of move- 

 ment the presence of other phenomena which are equally characteristic 

 of life and with which non-living material is not endowed? Prominent 



* The causation not only of movements but of various other manifestations of life 

 by alterations in surface tension of living substance is ably dealt with by A. B. Macallum 

 in a recent article in Asher and Spiro's Ergebnisse der Physiologic, 1911. Macallum 

 has described an accumulation of potassium salts at the more active surfaces of the 

 protoplasm of many cells, and correlates this with the production of cell-activity 

 by the effect of such accumulation upon the surface tension. The literature of the 

 subject will be found in this article. 



f G. F. Fitzgerald (Brit. Assoc. Reports, 1898, and Scient. . Trans. Roy. Dublin 

 Society, 1898) arrived at this conclusion with regard to muscle from purely physical 

 considerations. 



I ' Vital spontaneity, so readily accepted by persons ignorant of biology, is disproved 

 by the whole history of science. Every vital manifestation is a response to a stimulus, 

 a provoked phenomenon. It is unnecessary to say this is also the case with brute 

 bodies, since that is precisely the foundation of the great principle of the inertia of 

 matter. It is plain that it is also as applicable to living as to inanimate matter. '- 

 Dastre, op. cit., p. 280. 



