6 SCIENCE AND PHILOSOPHY OF THE ORGANISM 



variation of the medium or the organism, just as in the case 

 of regulation proper. 



An actual instance will give you perhaps a better idea 

 of what I am thinking of, than mere abstraction can do. 

 Take a dog and ask what characters resembling regulations, 

 if not regulations themselves, may occur in his movements. 

 The dog is running towards a certain place along the direct 

 line that leads to it, a carriage is crossing this line just 

 when the dog has to pass : the dog will run a little more 

 quickly and will make a curve in order to avoid the carriage. 

 Another dog has undergone an operation involving the loss 

 of a part of one hemisphere of the brain : at first his move- 

 ments are very defective, but after a certain time, as the 

 experiments of Goltz and others have shown, they become 

 much less so than they were immediately after the operation. 

 And a third dog is injured in one of his legs so that he is 

 forced to run on three legs only : yet he manages to reach 

 the place he wants to get to, by using his three legs in a 

 manner somewhat different from the normal. 



Here we have instances of all possible kinds of regulation, 

 or, if you prefer to say so, of the correspondence between 

 the sum of conditions and the sum of single effects con- 

 cerned in movement, which may occur in the field of motor 

 physiology, no matter by what means or organs movement 

 is carried out, be it by cilia, muscles, or threads of protoplasm. 

 In the first instance the dog's goal was reached, in spite of 

 a change in the outer conditions, by means of a change 

 in certain single acts of movement : the dog ran round the 

 carriage instead of following the straight line. In the 

 second instance we do not know very much about the 

 change of function that follows the change effected in the 



