MUSCULAR POWER. 119 



all occasions where considerable mechanical force 

 is wanted; just as in a great manufactory, where 

 an immense quantity of machinery is to be set in 

 motion, and a great variety of work is to be exe- 

 cuted, the human mechanist avails himself of some 

 constant moving force, such as that derived from a 

 fall of water, or from the expansion of steam. The 

 laws of inorganic matter furnish no force which 

 could conveniently have been appHed in the animal 

 body for that purpose ; but muscular power, from 

 its high intensity, is adequate to every object, and 

 has been accurately adjusted, by the most refined 

 application of the laws of mechanism, to all the 

 degrees and kinds of effects intended to be pro- 

 duced. 



Although the power be the same, yet the mode 

 of its application is exceedingly diversified ; and 

 the comparison of these diversities is the more in- 

 teresting, inasmuch as there are few of the animal 

 functions in which the ends to be answered are so 

 definite, and the operation of the expedients em- 

 ployed is so plain and intelligible. For while tlie 

 intricate chemical processes of the living system 

 generally elude our research, and the higher facul- 

 ties of sensation and perception are dependent on 

 still more recondite and mysterious powers of na- 



ments of the ribs in respiration ; the quick motions of the stamina 

 of the Berberis, Opuntia, and many plants of the genera Carduus, 

 and Centaurea ; the closing of the leaves of the Dioncea muscipula ; 

 and the shrinking of those of the Mimosa pudica, or sensitive plant. 

 On a superficial view, it must be acknowledged that these motions 

 bear a resemblance to the effects of muscular contractility ; but I 

 believe that naturalists are now generally agreed that there is no 

 real analogy between these phenomena, and that there is no sub- 

 stantial evidence for the existence of that property in the vegetable 

 kingdom. 



