ioo INTERPRETATION OF APPEARANCES \_CH.II1 



and the lower animals, many details are still in doubt, the same 

 visual appearances being quite differently interpreted by eminent 

 observers. 



Appearances which seem perfectly unmistakable with a low 

 power may be found erroneous or very inadequate, for details of struc- 

 ture that were undistinguishable with the low power may become 

 perfectly evident with a higher power or a more perfect objective. 

 Indeed the problems 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 watchful- 

 ness lest the appearances may be deceptive are thus admirably stated 

 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 directed, but even the most practiced observer is apt to 

 take no note of such phenomena as his mind is not prepared to ap- 

 preciate. Errors and imperfections of this kind can only be cor- 

 rected, it is obvious, by general advance in scientific knowledge; 

 but the history of them" affords a useful warning against hasty con- 

 clusions 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 conclu- 

 sions finally arrived at had been only attained after many modifica- 

 tions, or even entire alterations, of doctrine. 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 



