196 LIFE AND DEATH. 



The two orders of conditions, the one provided by the 

 being itself, the other by external agents, are equally 

 indispensable — and therefore of equal importance or 

 dignity. But they are not equally accessible to the 

 experimentalist It is not easy to exercise on the 

 organization direct and measurable actions. On the 

 contrary, the physical conditions are in the hands 

 and at the discretion of the experimenter. By them 

 he may reach the vital manifestations as they appear, 

 stimulate or check them, defer or precipitate them. 

 Thus, for instance, the physiologist suspends or re- 

 establishes at his will full vital activity in a multitude 

 of reviviscent or hibernating beings, such as grains, 

 the infusoria capable of ettcystment, the vibrio, the 

 tardigrade, the cold-blooded animals, and perennial 

 plants. 



The ambient world therefore furnishes to the animal 

 and to the vegetable, whole or fragmentary, those 

 materials of its organization which are at the same 

 time the stimuli of its vitality. That is to say, the 

 vital mechanism would be a dormant and inert 

 mechanism if nothing in the surrounding medium 

 could provoke it to action or give it a check. It 

 would be a kind of steam engine without coal and fire. 



Living matter, in other words, does -not possess real 

 spontaneity. As I have shown elsewhere, the law of 

 inertia which it is supposed it obeys with inert bodies 

 is not special to them. It is applied to the living 

 bodies whose apparent spontaneity is only an illusion 

 contradicted by physiology as a whole. All the vital 

 manifestations are responses to a stimulus of acts 

 provoked, and not of spontaneous acts. - 



Generalization of the Lazu of Inertia in Living 

 Bodies. Irritability. — In fact, vulgar prejudice opposes 



