Mechanistic Biology 243 



of technique, and technique is a dangerous thing on which to build 

 philosophical superstructures. On the contrary, the biochemist 

 has got along very well without the need of the neo-vitalist hypo- 

 thesis. If he accepts it, it means for him, among other things, 

 that he can never hope to get any approach to controlled conditions 

 in his experiments. The essence of the experimental method is to 

 keep all possible conditions constant in any one experiment, and to 

 vary that one so that its effect unembarrassed by any other effects 

 may be observed. If an entelechy is present in tissues and organs 

 the biochemist can never get controlled conditions, for he has no 

 means of telling what the entelechy may want to do next. But 

 the fact is, however, that by innumerable researches we know re- 

 sults may be repeated any number of times, that controlled condi- 

 tions can be attained, and that living matter in vitro does act as a 

 physico-chemical system. The neo-vitalist retires from this 

 position by pointing out that the entelechy acts only in the body 

 as a whole, and it is to his argument for the " actual wholeness " 

 of organisms that we must now turn. 



One aspect of this argument is the assertion that so far no com- 

 plete mechanical explanation of the functions of any one organ has 

 been advanced. There is very little in this statement, for no organ 

 or cell exists in and for itself ; it has relations with all the rest of the 

 body. Accordingly a complete mechanistic description of one unit 

 is impossible until all are so described. It is absurd, as has be6n said 

 elsewhere, " to expect biochemical investigators to deal exhaustively 

 with the brain or the kidney and then to proceed en masse to the 

 spleen." 



More important is the contention that the wonderfully delicate 

 regulatory powers of the organism are not seen until the organism 

 is studied as a whole. That is perfectly true, but then biochemists 

 and physiologists do study the body as a whole, and the more those 

 regulatory mechanisms are studied the more clearly mechanistic 

 do they become. The nice regulation of blood acidity is now 

 very fully understood and the processes of metabolism continually 

 demonstrate their dependence on mechanistic principles. 



Haldane also asserts that the tendency of the animal organism 

 to maintain its internal and external environment constant is the 

 fact about life which can never be explained on mechanistic grounds. 

 Apart from the implicit argument from inconceivability the fallacy 

 of which has already been pointed out above, this statement neglects 



