194 SYMBIOGENESIS 



Leaving it to the future to decide how large a share of 

 vital metamorphosis (of symbiogenesis !) is due to catalytic 

 action, and what kind of dynamics are here involved, Spencer 

 confines himself to the physical and chemical .behaviour of the 

 four chief elements (Oxygen, Hydrogen, Carbon, Nitrogen) 

 which " in various combinations make up living bodies." 



He notes the extreme chemical indifference shown by 

 nitrogen, and likewise the low stability and small activity of 

 the animal bases (albuminoids), such as urea, kreatine, 

 kreatinine, as compared with the stabilities and activities of 

 the simpler inorganic compounds. 



It is, in particular, the nitrogenous constituents of living 

 tissues albumen, fibrin, and casein, and their allies in which 

 that molecular mobility, exhibited by three of their com- 

 ponents in so high a degree, is reduced to a minimum. 



The chemical characteristics of these substances are instability and 

 inertness carried to the extreme. How rapidly albumenoid matters 

 decompose under ordinary conditions, is daily seen : the difficulty of 

 every housewife being to prevent them from decomposing. It is true 

 that when desiccated and kept from contact with air, they may be 

 preserved unchanged for a long period ; but the fact that they can only 

 be thus preserved proves their great instability. It is true, also, that 

 these most complex nitrogenous principles are not absolutely inert ; 

 since they enter into combinations with some bases; but their unions 

 are very feeble. 



We shall have to recur to the bio-dynamic significance of 

 the "nitrogenous principles." Meanwhile, we w r ill bear in 

 mind their important characteristics as apparent already in 

 Spencer's day. Spencer also provides some useful hints 

 towards an interpretation along general mechanical lines of 

 the role played by the physical peculiarities of the elements in 

 organic compounds. This is what, he says, an enquiry 

 promises to bring out : 



Proceeding on mechanical principles, it may be argued that the 

 molecular mobility of a substance must depend partly on the inertia of 

 its molecules ; partly on the intensity of their mutual polarities ; partly 

 on their mutual pressure, as determined by their aggregation, and (where 

 the molecules are compound) partly on the molecular mobilities of their 



