34 The Microscope 



jective, for example, with a X20 ocular gives a far less satisfactory image 

 than a X40 objective with a XlO ocular. 



Substage Condenser. This is just as important a part of the optical sys- 

 tem as is the objective. Nothing should be considered except an N.A. 

 1.4 achromatic condenser. 



Illuminating System. The lamp described for use with the medical mi- 

 croscope (Fig. 25) can be used with a research microscope. It is not 

 nearly so convenient, however, as the Ortho-Illuminator shown in Fig. 



35 and in Figs. 40 to 45, which the author regards as the greatest advance 

 in microscope illuminators of the last half century. This device, originally 

 introduced by Silge and Kuhne, but now marketed by the American 

 Optical Company, permits automatic Kohler illumination with almost 

 effortless ease in the control of centering and of light intensity. Many 

 microscopes with illuminating systems built into the stand give effortless 

 Kohler illumination and ease of centering, but the intensity can only be 

 controlled by a rheostat— a situation wholly disastrous if color photog- 

 raphy is to be attempted. 



Setting Up a Research Microscope. There is no point in trying to use 

 a research microscope that has not been properly adjusted. Many workers 

 obtain worse images from these extremely expensive systems than can 

 be obtained from a medical microscope simply because they do not know 

 how to cope with the multiplicity of adjustments necessary. The two 

 vital operations are centering the substage condenser and centering the 

 light source. It is assumed that the reader is completely familiar with 

 the operations described earlier in setting up a medical microscope. 



Centering the Substage Condenser 



1. Set the microscope approximately in place over the Ortho-Illumina- 

 tor (Fig. 40). Or set it up in front of a lamp as in Fig. 25. 



2. Make sure, if the substage iris is of the type shown in Figs. 36 and 37, 

 that it has been clicked into a central position. Then close the substage 

 iris as far as possible and rotate the X 10 objective into position. 



3. Focus up and down, using, if necessary, both the coarse adjustment 

 of the microscope and the rack of the substage, until the substage iris is 

 in focus. Make sure by opening and closing it that you are looking at 

 the substage iris, and not at some other iris in the system. 



4. Use the condenser centering screws (Figs. 38 and 41) to bring the 

 image of the iris into the center of the field. 



The substage condenser is now centered with the objective system, 

 provided the iris is properly centered with the condenser. Failure to find 

 an image of the substage iris is sometimes caused by using too powerful 

 an ocular and a X2 or X5 ocular is an extremely useful accessory to have 

 available if a X 10 apochromatic objective is being employed. 



