ABSORPTION. 83 



Ultimately these products, when not dissipated as 

 volatile, form nutriment for different generations and 

 kinds of putrefactive infusoria, till finally nothing 

 but a clear liquid is left, with a powdery sediment 

 composed of unconsumable matters and bacterial and 

 other germs. Thus in the course of successive genera- 

 tions is effected the reduction to simple compounds 

 which is performed simultaneously by the myriads 

 of plastids of different kinds which go to make up in- 

 dividuals of the higher orders. 



Absorption. In the absorption or retrograde 

 metamorphosis of the tissues, we have, at first 

 sight, a difficulty in the protoplasmic theory. 

 But on closer inspection it proves more capable 

 of explaining the phenomena than any other hypo- 

 thesis. For if all the tissues are merely dead 

 formed material and therefore passive, now are they 

 to undergo that renewal which implies removal of old 

 worn-out parts us well us deposition of new ? It is 

 true that by solution, oxidation, exosmosis, and other 

 chemical and physical processes, a certain amount 

 of effete matters is got rid of, as is allowed by Dr. 

 Beale also, yet that does not nearly account for the 

 bulk of the change in solid tissue which is supposed to 

 be continually going on. In most works on physi- 

 ology, it is tacitly assumed that although now the pro- 

 toplasm may be the chief agent, embryologically speak- 

 ing, for the production of the tissues, yet when once 

 formed they possess vitality, and are renewed, particle 

 for particle, by strictly vital processes as they are worn 

 out, although no distinct meaning is ever given to the 

 expression wear and tear as applied to living parts. 



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