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 

 impossible to do good microscopical work unless the microscope gives 

 and continues to give good definition and the working parts remain 

 firm. 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 fingers is 

 preferable. Therefore, the mechanical stage should be capable of 

 ready attachment or removal. A triple or quadruple nose-piece, 

 according to the number of objectives used, is also indispensable. 

 To meet the demands of clinical microscopy there should be three 

 objectives, preferably a 16 mm. (2/3 in.), a 4 mm. (1/6 in.) and a 

 2 mm. (1/12 in.) homogeneous oil immersion. The Zeiss AA is a 

 17 mm. objective, and the Leitz No. 3, an 18 mm. one. The Zeiss D 

 is about 4.2 mm. and the Leitz No. 6, a 4.4 mm. A dust-proof quad- 

 ruple 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. for urine and 

 blood counting, with a 1/8 in. for examining hanging-drop preparations 

 and for quick examination of blood smears). An apochromatic 

 objective costs about three times as much as an achromatic one and, 

 except in photographic work, has little if any advantage. 



As regards oculars (eye-pieces) a No. 2 and a No. 4 will best meet 

 the requirements. For high magnification a No. 8 may be of service. 



