II THE PROGRESS OF SCIENCE 121 



absent, are but dawning on the minds of the older 

 writers. 



Modern physiology sets forth as its chief ends : 

 Firstly, the ascertainment of the facts and condi- 

 tions of cell-life in general. Secondly, in compo- 

 site organisms, the analysis of the functions of 

 organs into those of the cells of which they are 

 composed. Thirdly, the explication of the pro- 

 cesses by which this local cell-life is directly, or 

 indirectly, controlled and brought into relation 

 with the life of the rest of the cells which com- 

 pose the organism. Fourthly, the investigation of 

 the phenomena of life in general, on the assump- 

 tion that the physical and chemical processes 

 which take place in the living body are of the 

 same order as those which take place out of it; and 

 that whatever energy is exerted in producing such 

 phenomena is derived from the common stock of 

 energy in the universe. In the fifth place, modern 

 physiology investigates the relation between phy- 

 sical and psychical phenomena, on the assumption 

 that molecular changes in definite portions of 

 nervous matter stand in the relation of necessary 

 antecedents to definite mental states and opera- 

 tions. The work which has been done in each of 

 the directions here indicated is vast, and the ac- 

 cumulation of solid knowledge, which has been 

 effected, is correspondingly great. For the first 

 time in the history of science, physiologists are 

 now in a position to say that they have arrived at 



