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Chapter TT. 

 the mechanical functions in zoophytes. 



§ 1 . General Observations. 



The mechanism of an organized being is designed 

 to fulfil various important objects. These we may 

 distinguish into two classes ; the one having refer- 

 ence to its internal welfare, the other to its rela- 

 tions with external bodies. The different parts of 

 its system must, in the first place, be mechanically 

 united and supported, as well as protected from 

 injurious external impressions; and they must at 

 the same time be so constructed as to admit of all 

 the internal movements, which the performance of 

 their functions renders necessary. They must, in 

 the second place, be madecapableof exerting upon 

 external matter the actions which conduce to their 

 well being ; and in order to enlarge their sphere of 

 action, they must have the power of transferring 

 the whole body from one place to another; or, in 

 other words, of effecting its progressive motio7i. 



The objects included in the first of these branches 

 of the mechanical functions are answered by the 

 organization both of the vegetable and the animal 

 systems : but those of the latter belong exclusively 

 to the functions of animal life. The power of lo- 

 comotion, more especially, constitutes the most 

 general and palpable feature of distinction between 

 these two classes of beings. A plant, during the 



