348 PHYSIOLOGICAL DEVELOPMENT. 



in the increase of their own oscillations, instead of passing it 

 on. Molecules which are unstable but which, in assuming 

 isomeric forms, absorb motion, will not readily propagate it ; 

 since it will disappear in working the changes in them. But 

 unstable molecules which, in being isomerically transformed, 

 do not absorb motion, and still more those which, in being 

 so transformed, give out motion, will readily propagate any 

 molecular agitation ; since they will pass on the impulse either 

 undiminished, or increased, to adjacent molecules. If 



then we assume, as we are not only warranted in doing but 

 are obliged to do, that protoplasm contains two or more 

 colloids, either mingled or feebly combined (since it cannot 

 consist of simple albumen or fibrin or casein, or any allied 

 proximate principle) ; it may be concluded that any mole- 

 cular agitation set up by what we call a stimulus, will diffuse 

 itself further along some lines than along others, if the com 

 ponents of the protoplasm are not quite homogeneously dis 

 persed, and if some of them are isomerically transformed 

 more easily, or with less expenditure of motion, than 

 others ; and it will especially travel along spaces occupied 

 chiefly by those molecules which give out molecular mo- 

 tion during their metamorphoses, if there should be any 

 such. But now let us ask what structural effects 



will be wrought along a tract traversed by this wave of 

 molecular disturbance. As is shown by those transforma- 

 tions that so rapidly propagate themselves through colloids, 

 molecules that have undergone a certain change of form, 

 are apt to communicate a like change of form to ad- 

 jacent molecules of the same kind — the impact of each 

 overthrow is passed on and produces another overthrow. 

 Probably the proneness towards isochronism of molecular 

 movements necessitates this. If any molecule has had 

 its components re-arranged, and their oscillations conse- 

 quently altered, there result movements not concordant with 

 the movements in adjacent untransformed molecules, but 

 which, impressing themselves on the parts of such untrans- 



