68 MOLECULAR CONSTITUTION 



are widely dissimilar. Thus, these two extreme contrasts, the one 

 between physical mobilities, and the other between chemical 

 activities, fulfil in the highest degree a certain further condition 

 to facility of differentiation and integration." 



The very fact, then, that organisable matter is, in the main, 

 compounded of elements with such dissimilar properties, affords a 

 strong d priori presumption that such organisable matter would be 

 most unstable, and most prone to undergo metamorphic changes 

 imder the influence of even slight changes of condition — such as 

 might operate without appreciable result upon the majority of 

 inorganic substances. The properties of the various pi-oteid sub- 

 stances which form the all-essential constituents of living tissues, 

 are found to correspond entirely with these d priori requirements. 

 This can scarcely be better shown than it has been by H. Spencer 

 when he wrote ' : — " It is, however, the nitrogenous constituents of 

 living tissues that display most markedly those characteristics of 

 which we have been tracing the growth. Albumen, fibrin, casein, 

 and their allies are bodies in which that molecular mobility exhi- 

 bited by three of their components in so high a degree is reduced 

 to a minimum. ... It should be noted, too, of these bodies, that 

 though they exhibit in the lowest degree that kind of molecular 

 mobility which implies facile vibrations of the atoms as wholes, 

 they exhibit in a high degree that kind of molecular mobility 

 resulting in isomerism, which implies permanent changes in the 

 positions of adjacent atoms with respect to each other. ... In 

 these most unstable and inert organic compounds, we find that the 

 atomic complexity reaches a maximum : not only since the four 

 chief organic elements are here united with small proportions of 

 sulphur and phosphorus, but also since they are united in high 

 multiples. The peculiarity which we found characterised even 

 binary compounds of the organic elements, that their atoms are 

 formed not of single equivalents of each component, but of two, 

 three, four, and more equivalents, is carried to the greatest 

 extreme in these compounds that take the leading part in 

 organic actions. According to Mulder, the formula of albumen 

 is io(C^oH3iN50„)+S2P. That is to say, with the sulphur and 

 phosphorus there are united ten equivalents of a compound atom 

 — containing forty atoms of carbon, thirty-one of hydrogen, five of 

 nitrogen, and twelve of oxygen : the atom being thus made up of 

 nearly nine hundred ultimate atoms." 



" Loc. cit. p. 12. 



