GENERAL CONSIDERATIONS AND CONCLUSIONS 289 



has been found only one general point of view, which if not absolute, 

 yet is the rule, to account for the eternal transformations of energy in 

 the living body. Only those combinations of causes take place that 

 are as favorable as possible for the welfare of the animal. This holds 

 true even when entirely new conditions are artificially introduced 

 into the living organism. What is more remarkable than that, even 

 in the highly organized mammal, there should be a regeneration of 

 the bile duct after its removal, or that after a large piece of a nerve 

 has been extirpated by a severe operation it should be again renewed? 

 . . . What is more surprising than that the organism should become 

 accustomed to the most diverse kinds of organic and inorganic poi- 

 sons? . . . And, finally, there are a number of facts that make good 

 the law that changes appear to be governed by no other principle 

 than the purpose of making certain the existence of the organism." 



Pfliiger's teleological law of causality is that " the cause of every 

 need of a living being is at the same time the cause of the fulfilment 

 of the need." Pfluger explains that the word "cause" is here intention- 

 ally chosen in order to bring out the necessary, lawful connection in 

 which the cause of each need stands in relation to the fulfilment of 

 that need. He adds that it would have been more correct, but less 

 pointed, to have said "motive" or "inducement" instead of "cause. " 



In order to illustrate what is meant by this law, the following 

 examples may be given. Food and water bring back the organism 

 to its normal condition. The absence of food in the body leads to 

 hunger, and this to the taking in of more food ; or, in other words, the 

 need of food leads to the search for food, or at least to the taking in 

 of food. The sexual desire, or the need to reproduce, brings about 

 the condition of the animal that leads to reproduction. A defect in 

 the valves of the heart leads to the enlargement of the right or the 

 left ventricle. The removal of one kidney leads to the hypertrophy 

 and increased function of the other. And although not explicitly 

 stated by Pfluger in this place, we may add to this list the removal 

 of a part of an animal, that leads to the regeneration of that part. 

 Pfluger further states that we are making no subtle distinction when 

 we point out that these phenomena, if looked at from the point of 

 view of purposeful acts, appear to have a teleological side. In reply 

 to this it may be stated, however, that in certain cases of regenera- 

 tion it can be shown that the result is entirely useless, or even injuri- 

 ous to the organism ; hence the teleological nature of the process is 

 entirely lost sight of, and we are the more ready to accept a simple 

 causal explanation of the phenomena. The best example of this 

 that I can give is the development of a tail at the anterior end of a 

 posterior piece of an earthworm. This process is not an occasional 

 one, but is constant. An example of an apparently useful result, so 



