394 LABILITY AND ENERGY IN RELATION TO PROTOPLASM. 



" Let us turn to consider a difficulty in connection with Dr. 

 Loew's hypothesis — a difficulty involved in the whole conception 

 of lability. The difficulty will be best explained by a concrete 

 example. " One of the most interesting labile atomic groups," 



says Dr. LOEW, " is the aldehyde group, — C^tt in which the 



oxygen exerts an attracting influence upon the hydrogen con- 

 nected with the carbon atom, this being generally tetravalent, 

 but sometimes only bivalent. The hydrogen atom is thus ever 

 oscillating between the carbon and the oxygen, as may be in- 

 dicated by the following formulae : — 



_C \H -C-O-H -C<^ -C-O-H 



(i) (2) (3) (4) 



" The hydrogen atom may be conceived as oscillating between 

 the carbon atom and the oxygen atom, as the contact-breaker of 

 a faradic battery oscillates between the electro-magnet and the 

 connecting point to the longer circuit. The defect in the analogy 

 we have chosen serves to point the difficulty of which we have 

 spoken. The oscillation of the contact-breaker depends on two 

 forces that alternately become effective in opposite directions, the 

 force of the electro-magnet overpowering the force of the spring, 

 and the force of the spring when the electro-magnet has ceased 

 to act. But can we find any similar play of alternating forces in 

 our hypothetically constructed labile compound ? It does not 

 seem so. It is certain that the attractive force between two 

 chemical atoms increases enormously as the distance between 

 the atoms diminishes. Let us suppose our hydrogen atom to be 

 placed initially between the oxygen atom and the carbon atom in 

 such a manner that the pull is equal in both directions. If the 

 hydrogen atom now moves in the direction of, say, the carbon 

 atom, the attraction of the carbon atom at once becomes much 



greater than that of the oxygen atom, and the — form should 



be permanently assumed. 



" Docs, then, Dr. LOEW conceive that in a labile group 

 something takes place analogous to the changes in the faradic 

 battery when the contact-breaker is vibrating ? that the move- 

 ment — to return to our example — of the hydrogen atom towards 

 the carbon atom brings about a state of molecular forces within 



