CHAPTER III 



INTERPRETATION OF APPEARANCES 



APPARATUS AND MATERIAL FOR CHAPTER III 



A laboratory, compound microscope (I 132); Preparation of fly's wing, 50 

 per cent glycerin; Slides and covers; Preparation of letters in stairs (Fig. 96). 

 Mucilage for air-bubbles and olive or clove oil for oil-globules ( 149-152). 

 Solid glass rod, and glass tube (? 157-159); Collodion ($ 159); Carmine, India 

 ink, or lamp black (? 161-163); Frog, castor oil and micro-polariscope ($ 164). 



INTERPRETATION OF APPEARANCES UNDER THE MICROSCOPE 



>5 142. 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. Any- 

 one can look into a microscope, but it is quite another matter to in- 

 terpret correctly the meaning of the appearances seen. 



It is especially important to remember that the more of the 

 relations of any 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 magnification will give in- 

 creased 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 under- 

 takes 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 



