THE lifp: of mattkk. 415 



yicl'eJ sfeeJx — Tlietv heroic defence — Nickel .steels ])resent this phe- 

 nomenon in iui exao-gerafed deg-ree. The altei'iiatioii of operations 

 which we have just described, which bring the various parts of an ordi- 

 nary steel rod into a tempered state, is not necessary with nickel steel. 

 The etiect is produced in the course of a single trial. As soon as 

 there is any narrowing at any point the alloy hardens at that precise 

 place; the striction is hardly marked; the movement is stopped at this 

 point to attack another feeble point, stops there again and attacks a 

 third, and so on; and finally the paradoxical fact appears that a rod of 

 metal which was in a soft state and could be considerably elongated 

 has now 1)ecome throughout its whole extent hard, fragile, and inex- 

 tensible like tempered steel. It is in connection with this fact that 

 M. C'has. Edward (xuillaume spoke of heroic I'csistance to rupture. 

 It would seem, in fact, as if the bar of nickel iron had reenforced each 

 weak point in proportion as it was menaced. It is oidy at the end of 

 these efforts that the inevitable catastrophe occurs. 



Effect of teutperatiirc. — When the temperature changes it is seen 

 that these nickel irons elongate or retract, modifying at the same time 

 their chemical constitution. But these effects, like those which occur 

 in the glass reservoir of a thermometer, are not acquired all at once. 

 They are produced rapidly for one part and more slowly for a small 

 remainder. Bars of nickel iron which have been kept at the same 

 temperature change gradually in length during the course of an entire 

 year. Can we ffnd a better proof of intestinal activity occurring in 

 a substance greatly differing from living matter^ 



Nature of the activity (fjiai-ticte-'i. — These are examples of the intes- 

 tinal activity that occurs in brute bodies. Besides, these facts that we 

 are citing merely to refute the assertion of Bichat relative to the 

 immutability of brute bodies and to show their iictivity l)ring us, in 

 addition, another proof. They show^ that this activity, like that of 

 animals, is a guard against foreign intervention, and that this guard, 

 again like that of animals, is adapted for the defense and preservation 

 of the brute mass. 



If we accord a special \alue to the adaptati^•e or teleological char- 

 acteristic of vital phenomena, a characteristic which is so eaiuly abused 

 in biological interpretations, we may also ffnd it again in the inanimate 

 world. To this end we may add to tlie preceding examples a last one 

 which is no less remarkable. This is the famous case of the photog- 

 raphy of colors after BecquereTs method. 



Photogra,2jhy of colors. — A grayish plate, treated with chloride or 

 iodide of silver and exposed to a red light, rapidly becomes red. It is 

 then exposed to green light and after passing through some dull and 

 obscure tints it becomes green. If w^e wished to explain this remark- 

 able phenomenon we could do no better than to say that the silver salt 

 protects itself against the light that threatens its existence; that light 



