484 GENERAL PHYSIOLOGY 



life is based, is conditioned by the existence of certain very labile 

 com]30unds, which stand next to the proteids and on account of 

 their elementary significance in life are best termed biogens. To 

 a certain degree the biogens are continually undergoing spon- 

 taneous decomposition, just as is the case with other organic bodies, 

 e.^.,prussic acid. But this decomposition is much more extensive, 

 if even slight external stimuli act upon the living substance. We 

 must imagine that by reason of the extremely active intramolecu- 

 lar vibration of the atoms, which is the cause of the labile con- 

 dition, certain atoms, partly spontaneously and partly as a result 

 of external commotions, come under the influence of others for 

 which they possess greater affinity than for their original neigh- 

 bours, and in this manner more stable groupings of atoms arise as 

 independent compounds. In this respect the biogens can be com- 

 pared to explosive substances, the atoms of which possess likewise 

 very labile equilibrium and which upon receiving violent shocks 

 explode, i.e., rearrange their atoms into more stable compounds ; 

 e.g., nitroglycerine or trinitrate of glyceryl, which is employed for 

 making dynamite, is decomposed by mechanical impulses or electric 

 shocks into water, carbonic acid, nitrogen and oxygen : 203115(0 

 N02)3 = SHjO-l-eOO^-l-eN-l-O. But, in contrast to other ex- 

 plosive bodies, we must evidently ascribe to the biogens the 

 peculiarity that in decomjDosition the whole molecule is not de- 

 stroyed, but that certain groups of atoms, which are formed 

 by rearrangement, are split off, while the residue is again 

 built up into a complete biogen molecule at the expense of the 

 materials found in its vicinity, just as in the manufacture of con- 

 centrated sulphuric acid ^ the nitrous acid formed from nitric acid 

 by the withdrawal of oxygen is rebuilt into nitric acid 

 with the aid of the oxygen of the air. The substances still pre- 

 sent in the living substance in addition to the biogens are merely 

 " satellites " of the biogen molecule, and either serve for its con- 

 struction or are derived from its transformations. Thus far no 

 substances have been made known in living matter, which can 

 stand in any nearer or more remote relations to the biogens. 

 Nevertheless, from the variety in the decomposition-products 

 that are excreted by different kinds of cells in metabolism, it 

 must be concluded with great probability that biogen molecules 

 have not in all cells exactly the same chemical composition, but 

 that there are various biogen bodies, and even that the biogens 

 not only of different cells, but of the various differentiations of the 

 same cell, such as exoplasm, myoids or contractile fibres, muscle- 

 fibrillge, cilia, etc., have different constitutions, although they agree 

 in essential structure. The biogens, therefore, are the real bearers 

 of life. Their continual decomposition and reformation constitutes 

 the life-process, which is expressed in the manifold vital phenomena. 



1 Cf. p. 125. 



