492 PROTOPLASM 



mechanism itself, though new evidence tends to show that they 

 also serve in the latter capacity (see page 466). 



The importance that enzymes, hormones, and the like have 

 assumed led Pauli to modify his statement that the proteins 

 alone display those specific properties that we term life, by saying 

 that the protein plays the more passive part as carrier of the 

 more active vital substances (which may themselves be protein). 

 This is, in a sense, true; but if we compare the concept with that 

 generally held for enzymes, we find that of the two components — 

 enzyme and coenzyme — of which enzymes are presumed to 

 consist, both are equally important; the one cannot function 

 without the other; furthermore, the carrier is specific. 



Before we continue with the discussion on the fundamental 

 nature of proteins in living matter, it may again be said (pages 

 9-10) that many biologists prefer not to regard any one substance 

 in protoplasm as the most fundamental and thus designate it 

 as the ultimate living substance. In saying that the proteins 

 "alone display the specific properties of life," we do not thereby 

 imply that they display all the properties of life nor that they can 

 display even a major part of these properties when alone. Proto- 

 plasm is a living system. The proteins are the chief constituents 

 of this system, but the system is alive only when water, fats, 

 salts, etc., are also present. 



Among the properties characteristic of protoplasm that are 

 due to its protein constituents is coagulation. 



Coagulation. — In the past, coagulation has been regarded as 

 incompatible with life, but we now have in living matter a 

 number of very interesting cases of what may be termed reversible 

 coagulation. The idea of the reversible coagulation of proteins 

 is also new chemistry. "When you can unhoil an egg" has been 

 humorously used by chemists as an expression of the impossible. 

 But apparently it has been done. Living matter has been doing 

 it ever since life began. Dormancy in seeds, over a period of 

 years, probably involves the coagulation of certain protein con- 

 stituents of protoplasm; it must therefore also involve the 

 reversal of these coagula at the time of germination through the 

 agency of enzymes. 



One cannot always be sure whether coagulation or merely an 

 increase in viscosity involving other changes has taken place; 

 thus, the experiment of Bayliss, in which he gave an amoeba an 



