170 CHEMICAL CORRELATION 



an unceasing flow of nervous impulses to every growing 

 part throughout the period of growth, and for no other 

 purpose than the regulation of that growth, would seem 

 to involve an excessive amount of nervous activity if any 

 simpler means of accomplishing the same result could 

 be found. 



Chemical Adjustors. — As a matter of fact, experi- 

 ment has shown that gradual adjustments in organisms 

 are made through the agency of chemical substances. 

 The great advantage of this method is that a chemical 

 regulator can be constantly present as a constituent of 

 the protoplasm, and so can exercise its influence continu- 

 ously and uniformly. That protoplasm is susceptible of 

 chemical stimulation has been pointed out repeatedly. 



Basic and Growth Metabolism Chiefly Affected. 

 — It is perhaps worth while to note that while chemical 

 regulation may afi'ect all the kinds of metabolism of which 

 organisms are capable, basic metabolism and the metab- 

 olism of growth appear to be most definitely subject to 

 this kind of influence. Functional metabolism, in con- 

 trast, is typically under the control of the nervous system. 

 When one considers that the utility of functional metab- 

 olism is the immediate adaptation of the organism to its 

 environment, it becomes clear that nervous regulation, 

 which brings about prompt reactions to environmental 

 changes, is on the whole better suited to the control of 

 active function than is the slower acting chemical 

 regulator. 



Chemical Correlation in Plants. — Reference was 

 made to this phenomenon at the close of Chapter XII. 

 Here only a few familiar illustrations will be cited. A 

 chrysanthemum plant if left to itself will produce many 

 buds, each of which will develop into a moderate-sized 

 chrysanthemum blossom. By destroying all these buds 

 but one a single large blossom can be obtained. Evi- 

 dently there i.s here in the plant some type of correlation 

 which, so far as we know, must be chemical. If the grow- 



