204 THE PHENOMENA OF MOTION 



The vital force appears as a moving force or 

 cause of motion when it overcomes the chemical 

 forces (cohesion and affinity) which act between the 

 constituents of food, and when it changes the posi- 

 tion or place in which their elements occur ; it is 

 manifested as a cause of motion in overcoming the 

 chemical attraction of the constituents of food, 

 and is, further, the cause which compels them to 

 combine in a new arrangement, and to assume new 

 forms. 



It is plain that a part of the animal body pos- 

 sessed of vitality, which has therefore the power of 

 overcoming resistance, and of giving motion to the 

 elementary particles of the food, by means of the 

 vital force manifested in itself must have a mo- 

 mentum of motion, which is nothing else than the 

 measure of the resulting motion or change in form 

 and structure. 



We know that this momentum of motion in the 

 vital force, residing in a living part, may be em- 

 ployed in giving motion to bodies at rest (that is, in 

 causing decomposition, or overcoming resistance), 

 and if the vital force is analogous in its manifesta- 

 tions to other forces, this momentum of motion 

 must be capable of being conveyed or communi- 

 cated by matters, which in themselves do not de- 

 stroy its effect by an opposite manifestation of force. 



Motion, by whatever cause produced, cannot in 

 itself be annihilated ; it may indeed become inap- 

 preciable to the senses, but even when arrested by 



