THE LIVING SUBSTANCE 9 



Attempts to differentiate between the living and the nonUving 

 in protoplasm date from the earliest investigators. Hanstein 

 distinguished between the active living protoplasm and the 

 passive, lifeless "metaplasm." Sachs called the former 

 "energid" and the latter "energid products." The term "meta- 

 plastic" (or "paraplastic") still persists for metabolic products 

 which are generally recognized as lifeless. Other biologists 

 speculating on this distinction have wandered far into the philo- 

 sophical field by postulating special vital bodies which give to 

 protoplasm the properties of life. Buffon and Verworn con- 

 ceived of gigantic molecules termed "biogens" which were 

 supposed to be the life-giving elements of protoplasm, the rest 

 of the material being presumably nonliving. Spencer postu- 

 lated "physiological units"; and Altmann, "bioblasts." In 

 this category, though referring more particularly to hereditary 

 units, belong the "gemmules" of Darwin, the "pangens" of 

 deVries, the "plastidules" of Haeckel, the "biophores" of Weis- 

 mann, and the "genes" of modern geneticists. Nageli's "idio- 

 plasm" theory, while speculative like the others, has the 

 advantage of resting on a chemical foundation which is in 

 harmony with certain known facts. He accounted for hereditary 

 traits by specific molecular orientation. This led further to a 

 conception of elementary units of structure or aggregates of 

 molecules, which Nageli termed "micellae" and which were 

 destined to play a prominent role in subsequent theories of proto- 

 plasmic and colloidal structure. 



Older ideas on what in protoplasm is living and what not have 

 been mostly discarded. The controversy has settled down to 

 two possibilities, viz., the presence of some one ultimate vital 

 substance, on the one hand, or, on the other hand, a mixture of 

 substances the individual components of which taken alone are 

 nonliving but combined constitute a living substance. (There 

 is always the third possibility that the constituents are nonhving, 

 while the life force itself is extramundane). If the first possi- 

 bility is true, then the vital substance is most probably protein in 

 nature. Leathes states that proteins are generally considered 

 the most important components of protoplasm. Pauli writes, 

 "There can be no doubt as to the central position of the proteins 

 in the organization of living matter. They alone display the 

 specific properties of life." The opinion prevails among many 





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