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THE AMERICAN NATURALIST [Vol. XLII 



activity, now in a state of rest, there is a constant chem- 

 ical and physical interplay between the two material con- 

 stituents, and a constant interchange between them and 

 the surrounding medium, in which the laws of osmosis 

 play a prominent part. The careful investigation of the 

 nature of these internal and external exchanges seems to 

 be illuminating many time-honored physiological enig- 

 mas, such as absorption, secretion, excretion and other 

 instances of the passage of substances through mem- 

 branes, the electrical phenomena of tissues, the nature 

 of the nerve impulse, the fertilization of the ovum, and the 

 general nature of chemical changes within protoplasm- 

 enigmas which have been constantly quoted in support of 

 the vitalistic conception. But we should not be tempted 

 by success along these liries to claim, as is sometimes done, 

 that the life process is merely ionic or electrical or osmotic 

 in nature. In investigating physiological problems by 

 the aid of modern physical chemistry, we seem to be 

 brought at times periously near the electron theory of 

 matter, and we are tempted to hazard the guess that 

 the establishment of that theory would place the physi- 

 ologist under renewed obligations to the physicist. 



The study of ferments, too, is assisting— strange, in- 

 numerable, intangible bodies of uncertain nature, which, 

 present in minute, almost imperceptible, quantities, seem 

 to facilitate vital chemical actions without entering di- 

 rectly into them. In the early years ferments were 

 recognized as mediating the processes of digestion, and 

 but few of them were known. Of late their number has 

 been enormously increased, and a corresponding number 

 of intracellular or extracellular chemical processes has 

 been ascribed to their action. Each lias its own specific 

 chemical reaction to facilitate, and, in many cases at least, 



into its constituents and the synthesis of those constitu- 

 ents into the complex substance. The ferments^ that 



