CH. III~\ INTERPRETATION OF APPEARANCES in 



more, one may, by taking a little pains, familiarize himself with the 

 special forms in his own eyes so that the more conspicuous at least 

 may be instantly recognized. 



§ 1 66. Miscellaneous Observations. — In addition to the 

 above experiments it is very strongly recommended that the student 

 follow the advice of Beale, p. 248, and examine first with a low 

 then with a higher power, mounted dry, then in water, lighted with 

 reflected light, then with transmitted light, the following: Potato, 

 wheat, rice and corn starch, easily obtained by scraping the potato 

 and the grains mentioned; bread crumbs; portions of feather. Por- 

 tions of feather accidentally present in histological preparations 

 have been mistaken for lymphatic vessels (Beale, 288). Fibers of 

 cotton, linen and silk. Textile fibers accidentally present have been 

 considered nerve fibers, etc. Human and animal hairs. Study 

 with especial care hairs from various parts of the body of the animals 

 used for dissection in the laboratory where you work. These are 

 liable to be present in histological preparations, and unless their 

 character is understood there is chance for much confusion and 

 erroneous interpretation. The scales of butterflies' and moths, es- 

 pecially the common clothes moths. The dust swept from carpeted 

 and wood floors. Tea leaves and coffee grounds. Dust found in 

 living rooms and places not frequently dusted. In the last will be 

 found a regular museum of objects. 



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

 and to observe it with varying illumination and under various con- 

 ditions of temperature, moisture, etc., in order to obtain a fairly ac- 

 curate and satisfactory knowledge of it, so much the more is it 

 necessary not to be satisfied it microscopical observation until every 

 means of investigation and verification has been called into service, 

 and then of the image that falls upon the retina, only such details 

 will be noted as the brain behind the eye is ready to appreciate. 



§ 167. Summary for Proper Interpretation. — To summar- 

 ize 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. 

 See the 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. 



