264 LIFE AND DEATH. 



to this internal activity of material bodies, to the 

 pursuit of stability. Wiedemann, Warburg, Tomlin- 

 son, MM. Duguet, Brillouin, Duhem, and Bouasse 

 have revived the old experimental researches of 

 Coulomb and Wertheim on the elasticity of bodies, 

 the effects of pressures and thrusts, the hammering, 

 tempering, and annealing of metals. 



The internal activity manifested under these cir- 

 cumstances presents quite remarkable characteristics 

 which cannot but be compared to the analogous 

 phenomena presented by living bodies. Thus have 

 arisen even in physics, a figurative terminology, and 

 metaphorical expressions borrowed from biology. 



Comparison of the Activity of Particles with Vital 

 Activity. Since Lord Kelvin first spoke of the fatigue 

 of metals, or the fatigue of elasticity, Bose has 

 shown in these same bodies the fatigue of electrical 

 contact. The term accommodation has been employed 

 in the study of torsion, and according to Tomlinson 

 for the very phenomena which are the inverse of 

 those of fatigue. The phenomena presented by glass 

 when acted on by an external force which slowly 

 bends it, have been called facts of adaptation. The 

 manner in which a bar of steel resists wire-drawing 

 has been compared to defensive processes against 

 threatened rupture. And M. C. E. Guillaume speaks 

 somewhere of " the heroic resistance of the bar of 

 nickel-steel." The term "defence" has also been 

 applied to the behaviour of chloride or iodide of 

 silver when exposed to light. 



There has been no hesitation in using the term 

 " memory " concurrently with that of hysteresis to 

 designate the behaviour of bodies acted on by 

 magnetism or by certain mechanical forces. It is 



