PHYSICAL METHODS IN PHYSIOLOGY 8i 



stood. In the past, mistakenly believing that the concepts of 

 physics had a finality not allowed to those of biology, the 

 physiologist has tended to put forward theories of vital pro- 

 cesses based upon an imperfect knowledge both of physics and 

 of the physical accompaniments of the vital processes them- 

 selves. When amino-acids had been combined to form poly- 

 peptides, some ardent spirits began to acclaim the synthesis of 

 the protoplasm of which the living cell is made, little heeding 

 the fact that all that had been achieved was the synthesis of 

 something not unlike the bodies of which the cell is made after 

 it has been killed. Progress has not come in that way, but 

 rather from the laborious process of cleaning up by physical 

 methods, slowly and laboriously, one corner after another of our 

 ignorance of the physical causes, or accompaniments of vital 

 activity. We can safely say that the physics of to-day has not 

 " explained," will not " explain," any of the more characteristic 

 of the phenomena of life ; whether the physics of to-morrow 

 will explain them only to-morrow will decide. The attempt, 

 however, has been valuable, in so far as it has made clear 

 where and how physical science can help in elucidating the 

 mysteries of the living creature. Advance will come from 

 investigating the physical causes, the physical accompaniments, 

 and the physical products of vital activity with all the tools, 

 mental and material, of the exact sciences. We do not know 

 where such advance will lead us — if we are wise we shall not 

 pretend to know ; but we may be sure that, if we follow the 

 main roads built by the exact sciences, we shall go straighter to 

 our goal than if we take to short-cuts of our own choosing. 



The living creature is much more difficult to investigate 

 than the non-living, chiefly because its continued normal 

 existence is possible only between very narrow limits ; the 

 living creature, moreover, like an eddy or a wave, is a process 

 and not a thing, and it is difficult to maintain the stability and 

 constancy of a process under any kind of experimental manipula- 

 tion or procedure. Thus it is that the progress of physiology 

 has depended largely on that of instrument design, by which 

 instruments have been made to suit the living tissue which 

 could not be coerced or adapted to existing ones. Indeed, it 

 is remarkable how physiology has attracted, or produced, such 

 men as Einthoven, Keith Lucas, or Bull, with a genius for 

 designing instruments for specific purposes. Moreover, modern 

 instruments and instrumental methods — the ultra-microscope, 

 the Rontgen rays, the sensitive galvanometer, the high-frequency 

 current, the electrical measurement of chemical, thermal, or 

 mechanical changes, and the systematic employment of photo- 

 graphic methods of recording — these have led to a far higher 

 degree of certainty in following, and in analysing the physical 

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