BACTERIOLOGY, BLOOD-WORK AND 

 ANIMAL PARASITOLOGY. 



CHAPTER I. 

 APPARATUS. 



THE MICROSCOPE. 



THE most important piece of apparatus for the laboratory worker 

 is the microscope. Very satisfactory microscopes can be purchased in 

 this country. Instruments of standard German make are in use in 

 many laboratories and appear to give general satisfaction. It is impos- 

 sible to do good microscopical work unless the microscope gives and 

 continues to give good definition and the working parts remain firm. 

 Folding microscope stands are now made which are perfectly satisfac- 

 tory, such instruments, however, have only the advantage of occupying, 

 less space in a case so that unless the question of compactness is involved, 

 as in an outfit for the military services or for a microscopist who travels 



about a great deal, the ordinary rigid horseshoe base is to be preferred. 





 A mechanical stage is almost a necessity in connection with blood- work and its 



use is advantageous in bacterial preparations. For the study of tissue sections the 

 moving of the slide with the ringers is preferable. Therefore, the mechanical 

 stage should be capable of ready attachment or removal. For the examination of 

 colonies growing in Petri dishes we also use the stage unencumbered with the me- 

 chanical stage. A triple or quadruple nose-piece, according to the number of 

 objectives used, is also indispensable. 



Objectives. To meet the demands of clinical microscopy there 

 should be three objectives, preferably a i6-mm. (2/3 -in.), a 4-mm. 

 (i/6-in.) and a 2-mm. (i/i2-in.) homogeneous oil immersion. The 

 Zeiss AA is a ly-mm. objective, and the Leitz No. 3, an i8-mm. one. 

 The Zeiss D is about 4. 2-mm. and the Leitz No. 6, a 4. 4-mm. A dust- 

 proof quadruple nose-piece with four objectives will be found a great 

 convenience (in addition to the 2/3 -in. and i/i2-in. objectives, a i/4-in. 



