4 APPARATUS. 



It is advisable to cultivate the use of both eyes in doing microscopi- 

 cal work. When using one eye the other should be kept open with 

 accommodation relaxed. It is this squinting of the unemployed eye 

 which so often fatigues. A strip of cardboard four or five inches long, 

 with an opening to fit over the tube of the microscope, leaving the other 

 end to block the vision of the unused eye, will prevent the strain. 

 This apparatus can be purchased in vulcanite. 



Direct sunlight or excessively bright light is to be avoided. If 

 such conditions must exist a w r hite shade or muslin curtain drawn 

 across the window is a necessity. Light from the north and from a 

 white cloud is the most desirable. The technic in connection with 

 proper illumination is probably more important than any other point; 

 unless the light is utilized to the best advantage, the best results cannot 

 be obtained. In examining fresh blood preparations or hanging drops 

 the concave mirror should be used and the light almost shut off bv the 

 iris diaphragm so as to give a contour picture. In examining a 

 stained blood or bacterial preparation, the Abbe condenser should be 

 properly focused so as to best illuminate the stained film. In many 

 instruments set-screws are provided which check the elevation of the 

 Abbe condenser when the proper focus is reached. Inasmuch as the 

 light from the condenser should come to a focus exactly level with the 

 object studied, it is evident that a fixed position for the condenser would 

 not answer when slides of different thickness were used. Always use 

 the plane mirror when examining stained bacterial or blood -films, as 

 a color image is desired. Ordinarily in examining tissue sections, the 

 Abbe condenser should either be put out of focus by racking down or 

 by the use of the concave mirror and the narrowing of the aperture of 

 the iris diaphragm. Swing-out condensers are now made which are 

 very convenient. The proper employment of illumination only comes 

 with experience, and one should continue to manipulate his mirrors, 

 diaphragm and condenser until the best result is obtained. Then 

 study the specimen. 



APPARATUS FOR STERILIZATION. 



For the purpose of sterilizing glassware, media and old cultures 

 there are three methods ordinarily employed. The hot-air sterilizer, 



