220 THE PHENOMENA OF MOTION 



carbonic acid are held together. A certain amount of 

 force would necessarily be prevented from assuming the 

 form of moving power, if it were to be expended in 

 overcoming chemical resistance ; for the momentum of 

 motion of the vital force is diminished by all obstacles. 

 But the conversion of the constituents of blood into 

 muscular fibre (into an organ which generates force) is 

 only a change of form. Both have the same composi- 

 tion ; blood is fluid, muscular fibre is solid blood. We 

 may even suppose that this change takes place without 

 any expenditure of vital force ; for the mere passage 

 of a fluid body into the solid state requires no manifes- 

 tation of force, but only the removal of obstacles, which 

 oppose that force (cohesion), which determines the 

 form of matter, in its manifestations. 



In what form or in what manner the vital force pro- 

 duces mechanical effects in the animal body is altogeth- 

 er unknown, and is as little to be ascertained by experi- 

 ment as the connexion of chemical action with the phe- 

 nomena of motion which we can produce with the galvan- 

 ic battery. All the explanations which have been attempt- 

 ed are only representations of the phenomenon ; they 

 are, more or less, exact descriptions and comparisons 

 of known phenomena with these, whose cause is un- 

 known. In this respect we are like an ignorant man, 

 to whom the rise and fall of an iron rod in a cylinder, 

 in which the eye can perceive nothing, and its connex- 

 ion with the turning and motion of a thousand wheels at 

 a distance from the piston-rod, appear incomprehensible. 



