CHAPTER XI 



Experimental biology continued. Mechanism versus vitalism. 

 Physico-chemistry of vital processes, metabolism of ani- 

 mals and plants. 



Is there one law for the living and another for the dead, 

 or is the universe a unit in its working and all matter gov- 

 erned by universal law ? The former is the contention of the 

 "vitalist," the latter of the "mechanist." What is life? 

 Is it some inscrutable process, controlled by a "vital prin- 

 ciple" operating outside the realm of physics and of chem- 

 istry ? Or is it merely a special expression of the forces which 

 control inorganic matter ? Our only answer to these ques- 

 tions is that we do not know. Neither the substance nor the 

 energy of life has ever been analyzed, and the only way in 

 which we can identify life is by its manifestations. What 

 are these manifestations, and what light if any do they throw 

 upon the ultimate nature of life itself? 



Firstly, what is the stuff of which living things are made? 

 An analysis of living substances or protoplasm is exceedingly 

 difficult if not impossible. In order to analyze it, it must be 

 killed, and the readiness with which protoplasm breaks down 

 into innumerable simpler substances leads us to suspect that 

 after protoplasm is killed it is protoplasm no longer, so that 

 we are analyzing not protoplasm at all, but something else. 

 Our analyses are sufficient to show us however that proto- 

 plasm contains the same elements of which inorganic matter 

 is composed, united into a marvellously complex whole. All 

 life is "of the dust, and turn(s) to dust again." The mani- 

 fold varieties of life which we know lead us to believe in as 

 great a variety of protoplasm which determines this variability 

 in living things. In spite of its variability however all proto- 

 plasm alike contains protein consisting of carbon, hydrogen, 

 nitrogen, oxygen and sulphur, without which it cannot exist. 

 Protein however is found outside of protoplasm in egg albu- 

 men for example and in the various albumens and globulins 

 of the blood. These substances while protoplasmic products 

 are not protoplasm itself ; hence we see that in its composition 

 at least Hying matter does not differ fundamentally from non- 

 living, since both contain the same materials. 



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