JN THE ANIMAL ORGANISM. 209 



duce in itself is conveyed to it from other quarters ; 

 and the vital force which is wanting to it, in order to 

 furnish resistance to external causes of disturbance, it 

 receives in the form of excess from another organ, an 

 excess which that organ cannot consume in itself. 



We observe further, that the voluntary and involun- 

 tary motions, in other words, all mechanical effects in 

 the animal organism, are accompanied by, nay, are de- 

 pendent on, a peculiar change of form and structure in 

 the substance of certain living parts, the increase or 

 diminution of which change stands in the very closest 

 relation to the measure of motion, or the amount of 

 force consumed in the motions performed. 



As an immediate effect of the manifestation of me- 

 chanical force, we see, that a part of the muscular sub- 

 stance loses its vital properties, its character of life ; 

 that this portion separates from the living part, and loses 

 its capacity of growth and its power of resistance. 

 We find that this change of properties is accompanied 

 by the entrance of a foreign body (oxygen) into the 

 composition of the muscular fibre (just as the acid lost 

 its chemical character by combining with zinc) ; and all 

 experience proves, that this conversion of living mus- 

 cular fibre into compounds destitute of vitality is accel- 

 erated or retarded according to the amount of force 

 employed to produce motion. Nay, it may safely be 

 affirmed, that they are mutually proportional ; that a 

 rapid transformation of muscular fibre, or, as it may be 

 called, a rapid change of matter, determines a greater 

 18* 



