BACTERIOLOGY, BLOOD-WORK AND 

 ANIMAL PARASITOLOGY 



CHAPTER I 

 APPAJRATUS 



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 satisfactory, 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 horse- 

 shoe 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 mov- 

 ing of the slide with the fingers 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 mechanical 

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

 is also indispensable. 



One should always use a magnifying glass or better a lens in a tripod or an apla- 

 natic^triplet in the study of microscopic objects, prior to examination with the mi- 

 croscope. A dissecting microscope is better for this purpose and is very useful in 

 dissecting mosquitoes, etc. In fact the dissecting microscope is almost essential in 

 the examination of helminthological and entomological specimens. Of particular 

 value is a stage forceps for orienting insects, especially mosquitoes, when examined 

 on the stage of either a compound or simple microscope. 



The following precautions should be observed to prevent injury to 

 the microscope: 



i. If the fine adjustment works through the arm of the microscope, always grasp 

 the instrument by the pillar which supports the stage. In those microscopes, how- 



