■i-t-l PHYSIOLOGICAL DEVELOPMENT. 



liquid to solid and from soluble to insoluble on the slightest 

 molecular disturbance — those albumenoid matters whiuh, as 

 we see in clotted blood or the coagulable lymph that is 

 poured out on abraded surfaces and causes 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 

 Dandelion, immediately begin to alter when the surrounding 

 actions alter, are to be everywhere considered as undergoing 

 modifications by modified conditions. Organic bodies, con- 

 sisting of substances that, as I here purposely remind the 

 reader, are prone bej'ond all others to change when the 

 incident forces are changed, we must contemplate as in all 

 their parts difierently changed in response to the difierent 

 changes of the incident forces. And then we have to re^ 

 gard the concomitant differentiations of their reactions as 

 being concomitant differentiations of their functions. 



Here, as before, we must take iijto 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, 

 produced 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. 



It is manifest that our data are so scanty that nothing 



