74 



SCIENCE- G OS SIP. 



ON THE NATURE OF LIFE. 



By F. J. Allen, M.A., M.D. 



{Continued from page 13.) 



"T" WAS travelling when Mr. Geoffrey Martin's 

 -*- article continuing the discussion on this 

 subject appeared ; I was therefore unable to reply 

 to it immediately ; but will now try to answer 

 certain of his objections to my views. 



Although neglect of the functions of nitrogen is 

 a prominent fault of the older school of biological 

 chemists, there is no ground for attributing to me 

 the opposite fault of neglecting the carbon. In 

 the publication (') referred to in my previous 

 paper I have carefully described its great function 

 as the storer of energy, its deoxidation and subse- 

 quent oxidation being the principal means of the 

 " energy traffic." I have also given my own views, 

 as well as those of other theorists, concerning the 

 mode in which the carbon is united to the nitrogen 

 and other elements in living and dead material 

 respectively. I must repeat, however, that lability 

 is a rare quality of carbon compounds, unless 

 nitrogen also be present ; and that the highest 

 lability is achieved when the nitrogen is combined 

 with oxygen as well as with carbon. 



The theory that nitrogen is the central or link- 

 ing element in living substance is not disproved, 

 but rather supported, by the facts which Mr. 

 Martin adduces against it. I have pointed out ( 2 ) 

 that " when nitrogen is the central or connecting 

 element between complex radicles, as in an amine 

 or an alkaloid, the properties are usually pro- 

 nounced ; whereas, when nitrogen is peripherally 

 situated, as in an amide, the properties are usually 

 indifferent." Considering how weak the chemical 

 attractions of nitrogen are, it is only to be ex- 

 pected that the greater the number of heavy 

 groups connected with it, the greater will be the 

 strain and consequent tendency to rupture. In 

 other words, the central situation of nitrogen 

 tends to produce chemical instability or lability. 

 In such a compound as we are describing, oxygen 

 behaves as a heavy radicle if connected with 

 nitrogen ; for the retention of oxygen by nitrogen 

 is rendered difficult by the counter-attraction 

 which the carbon, hydrogen, sulphur, &c, of the 

 same molecule exert on the oxygen. 



The nitrogenous products whose formulae Mr. 

 Martin quotes are dead substances with peripheral 

 nitrogen. Before the breakdown of the parent 

 living molecule, those nitrogen atoms formed the 

 connecting links by which the radicles held on 

 to the mass, and then the nitrogen was the 



(1) " Wbat is Life ? " Proc. Birmingham Mat. Hist, ami Philos. 

 Soe. vol. xi. part i., 1899. 



(2) Ibid. 



" central or linking element." Central nitrogen is 

 characterised by lability and life, peripheral 

 nitrogen by indifference and death. 



I have summed up my views with regard to the 

 structure of the active molecule of living substance 

 as follows : — " It is a molecule of enormous size, 

 and, so far as the dynamic ( 3 ) elements are con- 

 cerned, its various groups are linked together by 

 many nitrogen atoms, which are placed internally 

 out not in chain. It is not a proteid, a cyan- 

 compound, an amide, an amine, nor an alkaloid ; 

 but something that can yield some of these during 

 life, and others at its death. Death consists in the 

 relaxation of the strained relationship of the 

 nitrogen to the rest of the molecule. When thus- 

 the silver cord is loosed, the released groups fall 

 into a state of repose. Most of these groups are 

 proteids, in which the nitrogen is peripheral, triad, 

 and unoxidised, having yielded its oxygen to some 

 other element ; if, however, such a proteid mole- 

 cule be applied to a living cell, it can be linked on 

 again by its nitrogen, which thus once more 

 becomes central." 



My remarks on silicon do not admit of all the 

 interpretation which Mr. Martin gives to them. 

 As to silicon life, I raised no objection on the ground 

 of strong chemical reagents or high temperature, 

 all of which may be present in some parts of the- 

 universe but I objected to the suggestion that the- 

 chemistry of the silicates (as known to us) was 

 akin to life. Let it never be forgotten that the 

 great phenomenon of life is not chemical complexity,. 

 but the energy traffic. The deoxidation and sub- 

 sequent oxidation of carbon involves a very great 

 accumulation and dispersion of energy, whereas 

 the changes in silicates involve a comparatively 

 small transfer of energy. There may be some 

 element which under certain circumstances can 

 rob silicon of its oxygen as nitrogen robs carbon. 

 Such an action would involve a great accumulation 

 of energy in the new silicon compound, and by an 

 opposite chemical change the energy could be 

 expended in useful work. This is the kind of 

 silicon chemistry that we have to find before we- 

 can attribute to silicon a vital role comparable 

 with that of the dynamic elements. For many 

 years I have taught the possibility of such a 

 function of silicon, but have held it probable that 

 at high temperatures the energy traffic would be- 

 carried on more readily by certain other elements, 



(3) The elements nitrogen, oxygen, carbon, and hydrogen 

 may be called the " dynamic elements," because they are the- 

 chief agents in the energy traffic. 



