EXPERIMENTATION 



little information and may even be misleading. The frequency 

 distribution should be given and some figures relating to indiv- 

 iduals are often helpful in giving a complete picture. Graphs also 

 can be misleading and the data on which they are based needs 

 to be examined critically. If the plotted points on a graph are 

 not close together — that is, if the observations have not been 

 made at frequent intervak — it is not always justifiable to connect 

 them with straight or curved lines. Such lines may not represent 

 the true position, for one does not know what actually occurred 

 in the interval. There may, for instance, have been an unsuspected 

 rise and fall. 



Misleading experiments 



Some of the hazards associated with the use of reason, hypo- 

 thesis and observation in research are discussed in the appropriate 

 chapters of this book. As a corrective to any tendency to put 

 excessive faith in experimentation, it is as well here to remind 

 the reader that experiments also can at times be quite misleading. 

 The most common cause of error is a mistake in technique. 

 Reliance cannot be placed on results unless the experimenter is 

 thoroughly competent and familiar with the technical procedures 

 he uses. Even in the expert's hands technical methods have to be 

 constantly checked against known " positive " and " negative " 

 specimens. Apart from technical slips, there are more subtle 

 reasons why experiments sometimes " go wrong ". 



John Hunter deliberately infected himself with gonorrhoea to 

 find out if it was a distinct disease from syphilis. Unfortunately 

 the material he used to inoculate himself contained also the 

 syphilis organism, with the result that he contracted both diseases 

 and so established for a long time the false behef that both were 

 manifestations of the same disease. Needham's experiments with 

 flasks of broth led himself and others to believe that spontaneous 

 generation was possible. Knowledge at the time was insufficient 

 to show that the fallacy arose either from accidental contamina- 

 tion or insufficient heating for complete sterilisation. In recent 

 years we have seen an apparently weU-conducted experiment 

 prove that patulin has therapeutic value against the common cold. 

 Statistical requirements were well satisfied. But no one since has 



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