life: its nature, origin, and maintenance — -SCHAFER. 497 



complex actions which are characteristic of the more highly differ- 

 entiated organisms have been developed in the course of evolution 

 from the simple movements characterizing the activity of undiffer- 

 entiated protoplasm; movements which can themselves, as we have 

 seen, be perfectly imitated by nonUving material. The chain of 

 evidence regarding tliis particular manifestation of life — ^moA^cment — 

 is complete. Whether exhibited as the amoeboid movement of the 

 proteus animalcule or of the white corpuscle of our blood; as the 

 ciUary motion of the irifusorian or of the ciliated cell; as the con- 

 traction 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 can not but conclude that it is alike subject to and produced 

 in conformity mth the general laws of matter by agencies resembling 

 those which cause movements in lifeless material.* 



assimilation and disassimilation. 



It will perhaps be contended that the resemblances between the 

 movements of hving and nonliving matter ma}^ be only superficial, 

 and that the conclusion regarding their identity to which we are led 

 will be dissipated when we endeavor to penetrate more deeply into 

 the working of living substance. For can we not recognize along 

 witli the possession of movement the presence of other phenomena 

 which are equally characteristic of life and with which nonliving 

 material is not endowed ? Prominent among the characteristic phe- 

 nomena of life are the processes of assimilation and disassimilation, the 

 taking in of food and its elaboration.^ These, surely, it may be 

 thought, are not shared by matter which is not endowed with life. 

 Unfortunately for this argumetnt, similar processes occur character- 

 istically in situations which no one would think of associating with 

 the presence of life. A striking example of this is afforded by the 

 osmotic phenomena presented by solutions separated from one 

 another by semipermeable membranes or films, a condition which is 

 precisely that which is constantly'- found in hving matter.^ 



It is not so long ago that the chemistiy of organic matter was 

 thought to be entirely different from that of inorganic substances. 



' " 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 unneces- 

 sary 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. 



'The terms "assimilation" and "disassimilation" express the physical and chemical changes which 

 occur within protoplasm as the result of the intake of nutrient material from the circumambient medium 

 and its ultimate transformation into waste products which are passed out again into that medium; the 

 whole cycle of these changes being embraced under the term "metabolism." 



8 Ledue (The Mechanism of Life, English translation by W. Deane Butcher, 1011) has given many illus- 

 trations of this statement. In the report of the meeting of 1867 in Dundee is a paper by Dr. J. D. Heaton 

 (On Simulationsof Vegetable Growths by Mineral Substances) dealing with the same class of phenomena. 

 See also J. Ilall-Edwards, Address to Birmingham and Midland Institute, November, 1911. The condi- 

 tions of osmosis in cells have been especially studied by Hamburger (Osmotischer Druck und lonenlehre, 

 Wiesbaden, 1902-4). 



