MOLECULAR FORCES. 173 



tendency to generate new motion., new decomposition, and new 

 metamorphosis. Hence we also observe that in processes of the 

 highest vitality in the organs, the most decomposeable substances, 

 even self-decomposing bodies, are formed. Diastase, ptyalin, and 

 pepsin, the most readily decomposeable substances, are produced 

 only during high organico-vital activity ; but owing to the inces- 

 sant metamorphoses which they undergo, even whilst they are being 

 submitted to chemical investigation, they have been but imper- 

 fectly examined. It is not, therefore, the capacity for repose in 

 inert matter, on which the persistence of motion, and consequently 

 life, depends ; for the return of the molecules to a state of rest 

 is prevented in the same manner as falling when a man is walking 

 or running. The chemical molecules are not in a condition of 

 stable equilibrium or of the strongest'affinity ; but the act of falling, 

 the more constant union, the suspension of motion, is prevented 

 by another simultaneous motion, the centre of gravity becoming 

 unstable, and the manifestations of affinity being kept au courant. 

 In consequence of the variety of substances which are brought 

 into contact with one another during the metamorphosis of matter 

 in plants and animals, one molecular mass is hindered by another, 

 during the general motion and transposition, from attaining its 

 natural centre of gravity, and is constantly drawn aside into new 

 directions at the time it was striving to acquire equilibrium by the 

 most powerful forces of affinity. Many poisons destroy life merely 

 by suspending the action of some of the factors of organic motion ; 

 in the same manner as in fermentation and putrefaction^ the special 

 exciters of these processes induce chemical equilibrium. 



Organico-chemical motion is the most complicated of all mole- 

 cular changes ; for besides the many new substances formed at one 

 spot and at one time from other substances, there also occurs in 

 an equal degree a disturbance and a new arrangement of the 

 particles of the previously formed bodies. We may here instance 

 the muscular tissue, in which the muscular fibre is formed, and 

 where, after it has continued for some time to subserve the higher 

 purposes of life, it undergoes a new metamorphosis in the muscle, 

 simultaneously with the formation of new fibre. Thus we have 

 here, at one and the same spot, the beginning or origin of a sub- 

 stance, its persistence or adaptation, and its termination or disso- 

 lution. Occasionally, one or other of the factors of motion 

 becomes consolidated, without passing through the general course 

 of the ordinary phenomena ; an aggregation of molecules is here 

 brought to a state of chemical equilibrium, and forms a more con- 

 stant combination ; individual groups are brought into rest, and 



