330 THEORETICAL BIOLOGY 



He is as much averse to explaining the action of an animal 

 through its soul as he would be to inquiring into the soul 

 of a steam-engine. 



Nevertheless, he is nearer to biology than are other 

 physicists. For him the world does not consist of a hap- 

 hazard dance of atoms, but is filled with mechanisms and 

 machines, which fit exactly into one another. Loeb is much 

 too much of a professional as regards mechanical problems ever 

 to recognise the doctrine of adaptation. No one could ever 

 persuade him that a motor-car could develop out of a bicycle. 



He openly recognises the congruity of organisms one 

 with another and with their medium, without resorting to 

 hypotheses as to uncontrollable series of ancestors, and 

 accordingly he is an outspoken anti-Darwinian and an opposer 

 of Jennings. 



The mechanical side of the life-problem has in him its 

 most consistent and logical champion. In fighting this cause, 

 he tries to pursue his line of thought to its extreme, and 

 this readily brings him into opposition with well-known 

 biological facts. 



As a physicist, Loeb recognised from the outset that, 

 as preliminary to the understanding of the movements of 

 animal-machines, there must be exact knowledge of the steer- 

 ing. Now such of our machines as perform spontaneous 

 movements consist, without exception, of an apparatus that 

 is solely effector, capable of carrying out locomotion in a 

 determined direction only when external forces impart to it 

 the right guidance. Loeb, judging animal-machines from the 

 same point of view, looks for the factor in the external world 

 that shall do this for them. He finds these in the " directed " 

 forces of the external world, and primarily in light and 

 gravity, and accordingly attempts to explain the directed 

 movements of animals by two factors (i) the animal's loco- 

 motor apparatus and (2) the direction-giving agent outside. 



