24 THE BEGINNINGS OF IIFE. 



elude that in each case some slight difference of com- 

 position in these units, leading to some slight difference 

 in their mutual play of forces, produces a difference in 

 the form which the aggregate of them assumes.' 



When we suppose — not voluntarily, but on account 

 of facts otherwise inexplicable — that some such higher 

 combinations arise ^spontaneously' amongst the mole- 

 cules of organic matter contained within hermetically 

 sealed flasks, it must not be thought that we are 

 appealing to processes which are new and previously 

 unrecognized. On the contrary, chemists are perfectly 

 familiar with such ^ spontaneous ' combinations taking 

 place amongst the molecules of various complex sub- 

 stances. And, occasionally, these changes result in the 

 formation of isomeric compounds, differing from those 

 previously in existence by reason of their greater mole- 

 cular complexity, just as ' physiological units ' are sup- 

 posed to differ from the higher colloid molecules. As 

 instances of this kind of change, we may call attention 

 to the following well-known facts. Cyanate of ammonia 

 (C N2 H* O) in aqueous solution is converted by the aid 

 of heat, or ' spontaneously ' when left to evaporate at 

 a low temperature, into urea (C^N^H^O^). Cyanic 

 acid (C N H O) in aqueous solution is spontaneously 

 converted into cyanelide (C N H O) ^^ . Cyanimide 

 (CN^H^) at 150° C is converted into cyanuramide 

 (C 3 N 6 H 6). Common aldehyde (C 2 H * O) in aqueous 

 solution, with a mere trace of oil of vitriol, is changed 

 into an oily aldehyde (C^ H^^ qs). Anhydrous sulphuric 



