184 THE ANATOMY OF SCIENCE 



and I once more express the hope that in attack- 

 ing the infalHbility of categories I have not 

 seemed to intimate that they are the less to be 

 respected because they are not absolute. The 

 interaction between two bodies is treated by the 

 methods of mechanics; the interaction of a bil- 

 lion such bodies must be treated by the statisti- 

 cal methods of thermodynamics. They are the 

 same bodies and presumably follow the same be- 

 havior, but a great group of new phenomena 

 emerges when we study an immense number, and 

 by this we must mean merely that phenomena 

 appear that never would have been recognized 

 or dreamed of if the two bodies alone had been 

 studied. 



Now let me make my apology for venturing 

 to say that one of the most striking attributes 

 of living organisms is the transmission of ac- 

 quired characteristics. While the statement can 

 hardly be questioned if there is no implication 

 as to the mode or mechanism of acquiring the 

 characteristics in question, yet I have used a 

 phrase w^hich has long been the catchword in 

 one of the most bitter of biological controver- 

 sies. An animal during its life is constantly 

 changing in consequence of its habits and en- 

 vironment; for example, certain of its muscles 



