IN THE LAST HALF- CENTURY. 41 



and that it has practically proved their 

 value as guides to the discovery of new 

 truth. All three doctrines are intimately 

 connected, and each is applicable to the 

 whole physical cosmos. But, as might 

 have been expected from the nature of 

 the case, the first two grew, mainly, out 

 of the consideration of physico-chemical 

 phenomena ; while the third, in great 

 measure, owes its rehabilitation, if not 

 its origin, to the study of biological phe- 

 nomena. 



In the early decades of this century, a (l) Mo- 

 number of important truths applicable, in constitu- 

 part, to matter in general, and, in part, matter. 

 to particular forms of matter, had been 

 ascertained by the physicists and chem- 

 ists. 



The laws of motion of visible and tan- 

 gible, or molar, matter had been worked 

 out to a great degree of refinement and 

 embodied in the branches of science 



