932 



SCIENCE. 



[N. S. Vol. XI. No. 285. 



merous compounds are known which very 

 easily undergo a chemical change ; modern 

 chemistry defines them as labile (unstable) 

 compounds. Sometimes influences of a very 

 subtle nature suffice to cause migration of 

 the atoms in labile position to a more stable 

 position whereby an isomeric and more 

 stable product results. 



I have repeatedly pointed out that we 

 must distinguish between potentially labile 

 and kinetically labile compounds ; in other 

 words, between static labile and dynamic 

 labile.* To the former belong for example, 

 the explosive organic compounds, as nitro- 

 glycerole or certain diazo compounds, to the 

 latter aldehydes and ketones.f "While the 

 former are destroyed by chemical changes 

 either totally or partially, the latter furnish 

 numerous derivatives with great readiness, 

 or change easily by atomic migration or 

 by polymerization into isomeric or poly- 

 meric compounds. Many highly interest- 

 ing cases of chemical change by atomic mi- 

 gration within labile molecules are known, 

 but reference needs here be made only to 

 one of the simpler instances — the change of 

 ammonium cyanate into urea which is ac- 

 complished by merely heating the aqueous 

 solution of the former. 



Ammonium cyanate. Urea. 



O : C : K.NH, becomes O : C -^K 



* "JN ±±2 » 



This transformation is also of interest 

 from another point of view, as being the first 

 synthesis of an organic substance, accom- 

 plished by Woehler in 1828. 



ologists adhere to the old opinion of chemical identity 

 of proteins in the living and dead protoplasm. 



* The potential chemical energy in this discussion 

 does not refer to the energetic relation of the com- 

 pound to others, as in combustion, hut to the intra- 

 molecular relation between the atoms of the compound 

 itself. We may distinguish this as intramolecular 

 potential chemical energy. 



t The enzymes also belong to the dynamically labile 

 compounds, as I have pointed out in Science, Decem- 

 ber, 1899. 



The analogy of living matter to dynamic- 

 ally labile compounds is also elucidated by 

 the action of many poisons. Prussic acid, 

 diamidogen, hydroxylamine, have in mod- 

 erate dilutions at the ordinary temperature 

 no action whatever on dead protoplasm or 

 on the ordinary proteins, while they change 

 living protoplasm very easily to dead pro- 

 toplasm, a change induced by a chemical 

 attack, labile compounds being more easily 

 attacked by chemical agents than stable 

 ones. * 



The principle of chemical lability has not 

 yet been the object of close investigation 

 even by chemists, while physiologists have 

 ignored it altogether, and this may be the 

 reason that the necessity for assuming a 

 chemical difference between the proteins of 

 the living and of the dead protoplasm has 

 not found due consideration, although this 

 distinction is absolutely necessary for com- 

 prehending the chemical properties of living 

 protoplasm. The free chemical energy due 

 to the labile character of the proteids in the 

 living protoplasm leads to respiration and 

 since this energy cannot be produced after 

 those labile proteins have changed to stable 

 ones, respiration must cease also at the 

 moment of death. The heat produced by 

 respiration increases still further the oscil- 

 lations of the labile atoms in the plasma 

 proteins, in other words, it increases the 

 charge of chemical energy, and the most 

 complicated chemical work can now be car- 

 ried out, the specific construction of a pro- 

 toplast determining the kind and direction 

 of the work. The maintenance of the respi- 

 ration process is just as little due to a con- 



* A systematic toxicological review shows us among 

 other things that all compounds acting upon alde- 

 hydes and all that easily attack labile amido-groups 

 are poisonous for all kinds of living protoplasm which 

 fact led me to infer that the lability of the plasma 

 proteids is caused by the presence of aldehyde and 

 amido-groups within the same molecules. Compare: 

 A natural system of poisonous actions, Munich, E. 

 Wolfi, publisher. 



