Jennings, Uexkull o)i Physiolugy of Behavior. ^^^ 



ism at certain juiictures. Having abandoned (in favor of the con- 

 strnction of fictitious machines) the requirement of finding out what 

 are the real forces at work in organisms, of finding out Avhat machines 

 actually do exist (as determined by the test of verification), the 

 author finds himself in oi)p(>sition to physiology, which searches pre- 

 cisely for the real (verifiable) forces, imiterials and machines of 

 organisms. To escape this oj)position, v. Uexkiill renounces physiol- 

 ogy and all its works ; renounces finding out the causes of things, and 

 calls himself a biologist only ; biology he nuiintains has an entirely 

 different purpose from })hysiology. "We distinguish two sciences of 

 aninuitc nature; Physiology, which arranges her nniterials according 

 to causality ; Biology, which arranges her materials according to pur- 

 posiveness (Zweckmassigkeit)" (29, Vorwort). The purpose of biol- 

 ogy is to work out the plan according to Avhich the body is made up 

 and acts (33, pp. 10, 11, etc.). The inafcrials — the actual chemical 

 and physical substances, properties and forces — used in realizing the 

 plan, do not concern biology, but form the field of i^hysiology (28, 

 p. 370). Hence the biologist may content himself with schemata 

 which r('])roduce what the organism does, even though the organism 

 and the schenni are operated by different forces acting on different 

 materials in different arrangements. Thus "'When I for example lay 

 out the })lan of structure of a worm, and in so doing use any con- 

 venient jdiysical schema, it doesn't occur to me at all to touch ui)on 

 a physical problem. One may always think of any other force 

 as at work in the same object. I am not concerned with that. I 

 seek only for a fitting expression in order to luake the })lan of the 

 animal anscliaidlcli" (28, p. 377). The biologist need not concern 

 himself with causal questions; with i)hysiology. "It is therefore not 

 to be complained of if we biologists, who are asking about the func- 

 tions of animals, look with much coolness at the end problems of 

 ])hysiology" (28, p. 377). 



denouncing then a causal study for biology, and holding that 

 "Anschaulichkeit" or the demonstration of the production of proc- 

 esses in a machine-like way is the '""most essential of alT' things in 

 l)iological explanations, v. Uexkull naturally gets into serious ditfi- 

 culties when he confronts processes which he is unable to present as 



