THE INNER TISSUES OF ANIMALS. 353 



|j^rated state of the muscular colloid will be that which it 

 tends continually to assume — that into which it has an in- 

 creasing aptitude tjo pass when artificial paral3^sis has been 

 produced, as shown by Dr. Norris — that into which it lapses 

 completely in rigor mortis. The sensible motion generated 

 by the contraction can arise only from the transformation 

 of insensible motion. This insensible motion suddenly 

 yielded up by a contracting mass, implies the fall of its com- 

 ponent molecules into more stable arrangements. And there 

 can be no such fall unless the previous arrangement is un- 

 stable. From this point of view, too, it is pos- 

 sible to see how the hydro-carbons and oxy-hydro-carbona 

 consumed in muscular action, may produce their effects. It 

 was said, when exposing The Data of Biology, that non-nitro- 

 genous substance might evolve heat only when transformed 

 in the circulating fluids, " but partly heat, and partly another 

 force, when transformed in some active tissue that has ab- 

 sorbed it: just as coal, though producing little else but heat 

 as ordinarily burnt, has its heat partially transformed into 

 mechanical motion if burnt in a steam-engine furnace " 

 (§ 18) ; and recent inquiries make it clear that some such 

 relation exists."' Here a feasible modus operandi becomes 

 manifest. For these non-nitrogenous elements of food when 

 consumed in the tissues, give out large amounts of molecular 

 motion. They do this in presence of the muscular colloids 

 that have lost molecular motion during their fall in the stable 

 or contracted state. And from the molecular motion they 

 give out, may be restored the molecular motion lost b}' 

 the contracted colloids : these contracted colloids may 

 so have their molecules raised to that unstable state from 

 which, again falling, they can again generate mechanical 

 motion. 



* See account of experiments m<ade by Profs. Fick and Wislicenus, trans- 

 lated by Prof. Wanklyn in the Phil. Mag. for May or June, 1866. Sea 

 also an article by Prof. Frankland in the September number of the sam* 

 journaL 



