INTRODUCTION 



The laboratory exercises outlined in the following pages are 

 designed to introduce the student to the study of animal parasi- 

 tology. Normally, the work will be undertaken after a prelimi- 

 nary course in general zoology or biology and it is thus unneces- 

 sary to discuss at length the equipment to be used or methods of 

 study. 



A knowledge of the use of the compound microscope is assumed, 

 though any user of the instrument would profit by reading over 

 carefully the booklets on this subject which are furnished by 

 the makers. Certain elementary rules are so commonly ignored, 

 even by advanced and graduate students, as to need further 

 emphasis. 



Care of the Microscope. — It must be remembered that the 

 microscope is an instrument of precision and should be treated 

 as such. It should be protected from dust and from fluids. 

 The glass surfaces of the lenses must not be touched with the 

 fingers for that will soil them. There is probably no elementary 

 rule of microscope manipulation which is more commonly violated, 

 yet its validity is obvious. 



Students often have difficulty in determining the location of 

 dirt and films which cause indistinctness of the image. If the 

 fault is in the preparation the fact will be obvious if the slide 

 is observed carefully while being moved; if in the eyepiece, by 

 rotating it while looking through the microscope; if in the mirror 

 by moving it. 



Lenses should be cleaned carefully by breathing on them and 

 wiping with special lens paper (Japanese filter paper) or a clean 

 soft linen rag. If this is not sufficient moisten the edge of the rag 

 slightly with alcohol. If the cloudiness should be due to balsam 

 or an oily substance, it will be necessary to use a small amount 

 of chloroform or xylol but this must be done quickly to obviate 

 the possibility of these fluids penetrating and injuring the setting 

 of the lens. 



Care of Preparations. — In cleaning the cover glasses of pre- 

 pared slides be very careful not to exert pressure as the chances 



