MICROSCOPICAL DIAGNOSIS. 



The simple microscopes offered by dealers as "dissecting" micro- 

 scopes, frequently have one or more "Coddington's" as a part of 

 their outfit. 



While a single lens is all that is required to constitute a single 

 microscope, two lenses, at least, are required for the compound 

 microscope. One lens is required to form an enlarged image of the 

 object, hence called the objective; and another lens to magnify this 

 enlarged image, and as this lens must be placed nearer to the eye 

 than the former lens, it i^ called the eye-piece, or ocular. 



Thus the image is inverted. This, however, can be remedied 

 by placing between the objective and the eye-piece a set of lenses, 

 known as the erector. This causes the object to appear in its 

 natural position, as in the simple microscope. We cannot recom- 

 mend this accessory to either the novice or the expert. 



The stand of a compound microscope includes all the frame- 

 work to which the eye-piece and objective are attached. 



Stands are sold separately by many makers, although one or 

 more eye-pieces usually accompany them. This is very convenient 

 for the purchaser, for he is now free to make his own selection of 

 objectives. 



A stand usually consists of the following parts: 



The Base or Foot (Fig. i) "A," the part which gives support 

 to the rest of the stan'd. The base should be heavy enough to make 

 the instrument rest firmly on the table, especially when inclined for 

 the camera, and it should rest upon three points only, giving the tri- 

 pod form. 



The Body "B," that part to which the objective is attached. 

 It should be supplied with the "society screw," in order that any 

 standard English or American objectives may be used with it. 



The Draw-tube "C," which slides within the body. 



Nearly all the better stands are provided with single draw-tubes, 

 while some have double tubes, thus giving greater range of magni- 

 fying powers. 



The Arm "D," a support for the body. This is usually broken 

 by a joint, in order that the instrument may be inclined to any angle 

 with the horizon. 



The Collar "E," a tube surrounding the body. This is not 

 present on many stands. 



The Coarse Adjustment "F," for coarsely and quickly focusing 



