CHAPTER III 



INTERPRETATION OF APPEARANCES 



APPARATUS AND MATERIAL FOR CHAPTER III 



A laboratory, compound microscope ( \ 121 ); Preparation of fly's wing ; 50 per 

 cent, glycerin; Slides and covers; Preparation of letters in stairs (Fig. 89); 

 Mucilage for air-bubbles and olive or clove oil for oil-globules (is 136-139). Solid 

 glass rod, and glass tube {\ 144-146); Collodion (->, 146); Carmine, India ink, or 

 lamp black (ji 148-150); Frog, castor oil and micro-polariscope (§ 152). 



INTERPRETATION OF APPEARANCES UNDER THE MICROSCOPE 



§ 129. General Remarks. — The experiments in this chapter are 

 given secondarily for drill in manipulation, but primarily so that the 

 student may not be led into error or be puzzled by appearances which 

 are constantly met with in microscopical investigation. Anyone can 

 look into a microscope, but it is quite another matter to interpret cor- 

 rectly the meaning of the appearances seen. 



It is especially important to remember that the more of the relations 

 of an}' object are known, the truer is the comprehension of the object. 

 In microscopical investigation every object should be scrutinized from 

 all sides and under all conditions in which it is likely to occur in nature 

 and in microscopical investigation. It is best also to begin with objects 

 of considerable size whose character is well known, to look at them 

 carefully with the unaided eye so as to see them as wholes and in their 

 natural setting ; then a low power is used, and so on, step by step until 

 the highest power available has been employed. One will in this way 

 see less and less of the object as a whole, but every increase in magnifi- 

 cation will give increased prominence to detail, detail which might be 

 meaningless when taken alone and independent of the object as a 

 whole. The pertinence of this advice will be appreciated when the 

 student undertakes to solve the problems of histology ; for even after all 

 the years of incessant labor spent in trying to make out the structure 

 of man and the lower animals, many details are still in doubt, the 

 same visual appearances being quite differently interpreted by eminent 

 observers. 



