242 PHYSIOLOGICAL DEVELOPMENT. 



out on abraded surfaces and causing adhesion between 

 inflamed membranes, assume new forms with the greatest 

 readiness are to have their metamorphoses studied in con- 

 nexion with the influences at work. Those compounds which, 

 as we see in the quickly-acquired brownness of a bitten apple 

 or in the dark stains produced by the milky juice of a Dande- 

 lion, immediately begin to alter when the surrounding actions 

 alter, are to be everywhere considered' as undergoing modifi- 

 cations by modified conditions. Organic bodies, consisting 

 of substances that, as I here purposely remind the reader, 

 are prone beyond all others to change when the incident 

 forces are changed, we must contemplate as in all their parts 

 differently changed in response to the different changes of 

 the incident forces. And then we have to regard the con- 

 comitant differentiations of their reactions as being concomi- 

 tant differentiations of their functions. 



Here, as before, we must take into account two classes 

 of factors. We have to bear in mind the inherited results of 

 actions to which antecedent organisms were exposed, and to 

 join with these the results of present actions. Each organism 

 is to be considered as presenting a moving equilibrium of 

 functions, and a correlative arrangement of structures, pro- 

 duced by the aggregate of actions and reactions that have 

 taken place between all ancestral organisms and their envi- 

 ronments. The tendency in each organism to repeat this 

 adjusted arrangement of functions and structures, must be 

 regarded as from time to time interfered with by actions to 

 which its inherited equilibrium is not adjusted actions to 

 which, therefore, its equilibrium has to be re-adjusted. And 

 in studying physiological development we have in all cases 

 to contemplate the progressing compromise between the old 

 and the new, ending in a restored balance or adaptation. 



Manifestly our data are so scanty that nothing more 

 than very general and approximate interpretations of this 

 kind are possible. If the hypothesis of Evolution fur- 

 nishes us with a rude conception of the way in which the 



