44 A. E. HILTON ON THE NATURE OF LIVING ORGANISMS. 



condition, is found in the form of diamonds. That is significant, 

 but paradoxical. "Life is colloidal," we say; " death is crystal- 

 lised " : yet in a diamond, one of the most perfect crystals, we 

 have the very element most necessary to organic life. The 

 truth is that its power of hard crystallisation, when pure, is an 

 indication of the tenacity with which, although much modified, 

 it holds its own atoms when it forms compounds with other 

 substances. To the highly plastic plasm carbon gives stability, 

 by maintaining the substantial integrity of the molecules when 

 atomic groups of other elements are disintegrated. According to 

 the theory of compound radicals, on which organic chemistry is 

 built up, groups of atoms in the carbon compound molecule may 

 be replaced by groups of other atoms without impairing its 

 general character; and this changeless changeableness is a 

 peculiarly essential quality of sensitive living matter, in which 

 small alterations in arrangements of atoms often produce great 

 differences in properties. 



Another feature of carbon which qualifies it for its prominent 

 place in the organism is its desultoriness. Inorganic compounds 

 usually react rapidly and decisively ; but under such conditions, 

 life would be impossible. Carbon, on the contrary, is somewhat 

 inert, and combines with other elements in a hesitating, dilatory, 

 rambling kind of way, forming in a wandering fashion innu- 

 merable compounds w T ith but few materials, and at the same time 

 largely maintaining its own character. Its power of holding other 

 atoms in various combinations with its own is extraordinary, 

 the compounds of carbon with hydrogen, oxygen, and nitrogen 

 numbering 20,000 at least. These elements are all contained in 

 plasm, in which innumerable changes are constantly going on ; 

 but owing to the sluggishness of the carbon, the reactions are 

 often incomplete. Instead of passing on to finality, which would 

 mean death, the processes are arrested, or even reversed, and the 

 vital equilibrium is preserved. 



This reversibility of processes which occur in plasm is of great 

 importance. A familiar example of a reversible process is fur- 

 nished by a jelly, which liquefies when heated, and sets again on 

 cooling ; and the illustration is to the point, because there is no 



