Animal Morphology. 81 



Here, in this low form of animal life, we see an action 

 going on quite contrary to either syphonic action, capil- 

 lary attraction, or exosmosis, etc. It is marked by intervals 

 of intermission, and answers to nothing but a species of 

 alternate relaxation and contraction ; the effect is the inter- 

 preter of the cause. No direct observation can discover in 

 the sarcode, or jelly, muscular structure, but the effect tells 

 us that the fluid suffers compression at one time and is free 

 from it at another time. 



Again, in polypiphera many motions performed by these 

 low types of animal life can only be explained upon the 

 supposition of their having contractile power within them- 

 selves, though muscular structure cannot be detected in 

 their organism. 



Hence it is inferred that long before real muscle appears 

 a contractile power exists the result of material organism, 

 which starts motion independent of the ordinary surrounding 

 physical forces, though itself the result of special material 

 adjustment of molecules with molecules of a given and 

 definite character. 



It is only after very great and highly-modified cell differen- 

 tiation that we find cell architecture isolating the contrac- 

 tile membrane into a distinct structure, and assuming the 

 true character of muscle. 



Again, that which constitutes high and low forms of 

 animal life appears to be, the number of tripartite mem- 

 branes which are distinct the one from the other, in one 

 living organism, and, by a wonderful adaptation in morpho- 

 logy, mutually blend with each other. 



A brief enunciation of them, as belonging to man and 

 mammalia, will be first given, with this proviso that 

 connective tissue, though the most useful in all the body, 

 and ready to lend a helping hand in all difficulties as 

 a supernumerary, yet in differentiation is at par, and 



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