CHAPTER I 



APPARATUS 



The microscope is the most important piece of apparatus. It should 

 have a rack and pinion coarse adjustment, a fine adjustment, two 

 eyepieces magnifying about 5 and 10 diameters, a low-power objective 

 of about 16-mm. focus, and a high-power objective of about 4-mm. 

 focus, a double nosepiece, an iris diaphragm, and an Abbe condenser. 

 A cheap and practical form is shown in Figure 1, and similar instru- 

 ments are for sale by all the leading companies. 



The rest of the apparatus is for getting material ready for observa- 

 tion with the microscope. The following list includes only the appa- 

 ratus necessary for making preparations: a microtome; a razor; a 

 hone and a good razor strop; a paraffin bath; a turntable; a scalpel; a 

 pair of needles; a pair of scissors; a pair of forceps; staining-dishes ; 

 soHd watch glasses; bottles; a graduate (50 or 100 c.c); pipettes; 

 slides, 1X3 inches; round covers, 18 mm. or f inch in diameter; and 

 square covers, | inch. Longer covers will be needed for some of the 

 serial sections. 



Keep the apparatus clean, especially the microscope. Since the 

 chemicals used in histological technique are likely to damage the 

 stage and substage of the microscope, it is well to place upon the 

 stage a piece of glass 3 or 4 inches square. A lantern-slide cover is 

 just right for this purpose. It is not necessary to fasten it to the stage, 

 since it is merely for protection while examining slides which are wet 

 with reagents. In our own laboratory we use for examining wet slides 

 a cheap microscope with only a single low-power objective and a single 

 ocular. 



Some knowledge of the structure and optics of the microscope is 

 necessary if one is to use it effectively. Why are there so many dia- 

 phragms? Why is there an arrangement for raising and lowering the 

 condenser? Why does the mirror bar swing? Why is one side of the 

 mirror plane and the other concave? Everyone who uses even a cheap 

 microscope should know the answers to questions like these. All the 

 leading manufacturers furnish, free of charge, booklets, explaining 



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