CH. Ill ] IN TERPRE TA TION OF A PRE A RANCES. 8 1 



dent with a higher power or a more perfect objective. Indeed the prob- 

 lems of microscopic structure appear to become ever more complex, for 

 difficulties overcome by improvements in the microscope simply give 

 place to new difficulties, which in some cases render the subject more 

 obscure than it appeared to be with the less perfect appliances. 



The need of the most careful observation and constant watchfulness 

 lest the appearances may be deceptive are thus admirably stated b3 T Dal- 

 linger (See Carpenter-Dallinger, pp. 368-369) : ' ' The correctness of 

 the conclusions which tlie 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 directed, but even the most prac- 

 ticed 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 knowl- 

 edge ; 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 gen- 

 erally appear that the stability and completeness of the conclusions fin- 

 ally arrived at had been only attained after many modifications, or even 

 entire alterations, of doctrine. And it is therefore of such great impor- 

 tance 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 possi- 

 ble. 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 conclusions 

 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 researches. 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 prac- 

 tical wisdom ; and it is one which the microscopist cannot too soon learn 

 or too constantly practice." 

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