CHAPTER IV 

 INTERPRETATION OF APPEARANCES 



§ 186. Apparatus and material for Chapter IV. 



1. Laboratory compound micro- 8. Solid glass rod and glass tube 

 scope (fig. 2$). (§ 202). 



2. Preparation of fly's wing (§ 188). 9. Collodion (§204). 



3- S°% glycerin (§ 202). 10. Carmine, starch, chalk dust 



4. Slides and covers (Ch. X). (§ 206). 



5. Preparation of letters in stairs 11. Frog (§ 209). 



(fig. 66). 12. Castor oil (§ 209). 



6. Gum arable mucilage for air 13. Micro-polariscope (Ch. VIII). 

 bubbles (§ 194). 14. Fine forceps (fig. 70). 



7. Oil or milk for oil globules 15. Eosin (§ 202). 

 (§ 197)- 



§ 187. Appearances which seem perfectly unmistakable with a 

 low power, may be found erroneous or very inadequate with high 

 powers ;^ for details of structure which cannot be seen with a low power 

 may become perfectly evident with a higher power or a more perfect 

 objective. On the other hand, the problems of microscopic structure 

 become more and more complex with increased precision of investi- 

 gation and more perfect optical appliances, for structures that appeared 

 intelligible with a less perfect microscope may show complexities in 

 their details of structure with the more perfect microscope which 

 open up an entirely new field for interpretation. 



One must always be on the lookout for errors in judgment induced 

 by color effects due to purely optical means and to color in the speci- 

 men and also to avoid confusing refraction, reflection, and diffraction 

 effects with pigments, or actual structures of any kind. It is not infre- 

 quent in searching for malarial pigment in the red blood corpuscles 

 to mistake the dark-looking crenations on the corpuscles for the 

 pigment sought (§ 187a). 



The need of the most careful observation and constant watchful- 

 ness lest the appearances may be deceptive is thus admirably- stated 



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