io8 INTERPRETATION OF APPEARANCES [Ch. IV 



by Dallinger (see Carpenter-Dallinger, p. 427): "The correctness of 

 the conclusions which the microscopist will draw regarding the nature 

 of any object from the visual appearances which it presents to him 

 when examined in the various modes now specified will necessarily 

 depend in a great degree upon his previous experience in microscopic 

 observation and upon his knowledge of the class of bodies to which the 

 particular specimen may belong. Not only are observations of any 

 kind liable to certain fallacies arising out of the previous notions 

 which the observer may entertain in regard to the constitution of 

 the objects or the nature of the actions to which his attention is di- 

 rected, but even the most practised observer is apt to take no note 

 of such phenomena as his mind is not prepared to appreciate. Errors 

 and imperfections of this kind can only be corrected, it is obvious, by 

 general advance in scientific knowledge; but the history of them affords 

 a useful warning against hasty conclusions drawn from a too cursory 

 examination. If the history of almost any scientific investigation 

 were fully made known, it would generally appear that the stability 

 and completeness of the conclusions finally arrived at had been only 

 attained after many modifications, or even entire alterations, of doc- 

 trine. And it is therefore of such great importance as to be almost 

 essential to the correctness of our conclusions that they should not be 

 finally formed and announced until they have been tested in every 

 conceivable mode. It is due to science that it should be burdened 

 with as few false facts [artifacts] and false doctrines as possible. It 

 is due to other truth-seekers that they should not be misled, to the 

 great waste of their time and pains, by our errors. And it is due to 

 ourselves that we should not commit our reputation to the chance of 

 impairment by the premature formation and publication of conclu- 

 sions which may be at once reversed by other observers better 

 informed than ourselves, or may be proved fallacious at some future 

 time, perhaps even by our own more extended and careful re- 

 searches. The suspension of the judgment whenever there seems 

 room for doubt is a lesson inculcated by all those philosophers who 

 have gained the highest repute for practical wisdom; and it is one 

 which the microscopist cannot too soon learn or too constantly 

 practise." 



