324 PROGRESS OF SCIENCE IN THE CENTURY. 



terj ever recedes as we pursue it further into the re- 

 cesses of organisation." 



It may seem strange to ask whether the progress of 

 nineteenth century physiology has been signalised by 

 the achievements of re-expressing any vital phenom- 

 ena in terms of physics and chemistry. But it is, to 

 say the least, very doubtful that there has been any 

 such success. Leaving out of sight all phenomena, 

 like the bursting of a dry pea-pod, or the projection 

 of an image by the lens of the eye, which cannot be 

 called vital, we press the question whether the con- 

 traction of a muscle or the movement of a sensitive 

 plant, the flow of the blood or the ascent of sap, the 

 respiratory changes in a lung or in a leaf, the ab- 

 sorption of food from the intestine or the formation 

 of starch in a plant, — or any vital process can be 

 completely described in chemical or physical terms. 

 ITo doubt, chemical and physical processes have been 

 detected, and have been followed out in some cases 

 with great success, but has a complete redescription 

 in chemical or physical terms ever been attained? 

 ^^ To me,'' Bunge says,* " the history of physiology 

 teaches the exact opposite. I think the more thor- 

 oughly and conscientiously we endeavour to study 

 biological problems, the more are we convinced that 

 even those processes which we have already regarded 

 as explicable by chemical and physical laws, are in 

 reality infinitely more complex, and at present defy 

 any attempt at a mechanical explanation." 



Dr. J. S. Haldane goes even further : — " If we 

 look at the phenomena which are capable of being 

 stated, or explained in physico-chemical terms, we 

 see at once that there is nothing in them character- 

 istic of life. . . . We are now far more definitely 

 * Op. cit, p. 3. 



