CH. Ill] INTERPRETATION OF APPEARANCES. 91 



ciation of Wool Growers, 1875, p. 470, Proc. Amer. Micr. Soc, 1884, 

 pp. 65-68. 



For different appearances due to the illuminator, see Nelson, in Jour. 

 Roy. Micr. Soc, 1891, pp. 90-105 ; and for the illusory appearances due 

 to diffraction phenomena, see Carpenter-Dallinger, p. 376. 



If it is necessary to see all sides of an ordinary gross object, and to 

 observe it with varying illumination and under various conditions of 

 temperature, moisture, etc., in order to obtain a fairly accurate and 

 satisfactory knowledge of it, so much the more is it necessary not to be 

 satisfied in microscopical observation until every means of investigation 

 and verification has been called into service, and then of the image that 

 falls upou the retina, only such details will be noted as the brain behind 

 the eye is ready to appreciate. 



To summarize this chapter and leave with the beginning student the 

 result of the experience of many eminent workers : 



1. Get all the information possible with the unaided eye. Seethe 

 whole object and all sides of it, so far as possible. 



2. Examine the preparation with a simple microscope in the same 

 thorough way for additional detail. 



3. Use a low power of the compound microscope. 



4. Use a higher power. 



5. Use the highest power available and applicable. In this way one 

 sees the object as a whole and progressively more and more details. 

 Then as the object is viewed from two or more aspects, something like 

 a correct notion may be gained of its form and structure. 



