THE WORLD OF LIVING ORGANISMS i6i 



an animal in their relation to the world as it regards human 

 tools, whereas biology regards them as human tools that 

 become effective in conformity with plan only when they are 

 fitted into the surrounding- world. 



INTER-AD J USTMENT 



In considering the inner world of animals, we have learnt 

 to distinguish between mark-rule and action-rule. These two 

 rules constitute only portions of the general plan that is 

 expressed in the whole structure and in all the actions of 

 animals. We have seen that organs are fitted into one 

 another like the parts of a machine, and so we have spoken 

 of framework. But there can be no doubt that this entire 

 framework is likewise subject to a rule. This rule is 

 manifested so clearly in the permanent anatomical frame- 

 work that we need not discuss it further. On the other 

 hand, we must seek for the rule of inter-adjustment, when 

 the effectors, as they deal with the things of the external 

 world, create a temporary framework. 



As a matter of fact, in the world of action we are dealing 

 with a temporary framework of this kind, which becomes 

 apparent only when the animal shows activity in one of its 

 function-circles. The most obvious inter-adjustment is that 

 which connects the effectors of animals with the medium. 

 Merely by looking at these, we can teU whether we have to 

 do with an animal belonging to the air, to the water, or to 

 the land. Fins, wings and feet bear the unmistakable imprint 

 of their vocation. The more closely the function is confined 

 to a narrowly circumscribed medium, the more clearly can we 

 recognise from the effectors to what it is they are adjusted. 

 We distinguish feet that act as suckers, feet for running, feet 

 for leaping, and feet for climbing, and these give us a secure 

 basis whence we m.ay proceed to further classification of land 



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