INTRODUCTION TO MICROSCOPIC 

 TECHNIC. 



I. THE MICROSCOPE AND ITS ACCESSORIES. 



A detailed description of the microscope and its accessory appa- 

 ratus hardly lies within the scope of this book. If, notwithstanding, 

 a few points be touched upon, it is done only that the beginner 

 may have a working knowledge of the different parts of the instru- 

 ment which he must use. A more intimate knowledge of the theory 

 of the microscope may be acquired by studying such works as 

 those of Dippel, A. Zimmermann, and Carpenter. 



Histologic specimens are examined with the aid of the micro- 

 scope, an instrument which magnifies the objects by means of its 

 optic apparatus. For this purpose simple microscopes, consisting 

 of one or more converging lenses or lens systems may be used, 

 though they generally do not give sufficient magnification to be of 

 much service in the study of histologic specimens ; they give an 

 erect image of the object observed. When greater magnification 

 is desired, it is necessary to use a compound microscope, consist- 

 ing generally of two or more lens systems, giving an enlarged, 

 inverted, real image of the object observed. The lens system of a 

 compound microscope may be changed according to the needs of 

 the case, and thus a variation in the magnification of the object 

 obtained. The rest of the instrument consists of a framework 

 called the stand, the lower portion of which consists of a foot- 

 plate or base. From the base rises the column or pillar, to 

 which the other parts of the microscope are attached. From below 

 upward come the movable mirror, the stage and substage with 

 diaphragm and condenser, and the tube with pinion and fine adjust- 

 ment. One side of the mirror is concave, and serves to concentrate 

 the rays of light in the direction of a central opening in the stage. 

 The other side is plane. If the objects are to be examined by 

 direct illumination, and not by transmitted light, the mirror is so 

 placed that the rays are reflected away from the opening in the stage. 

 The specimen to be examined is placed on the stage, over 

 the central opening. If the light be too strong, the opening may 

 be diminished in size by means of a diaphragm. In some instru- 

 ments these diaphragms are placed in the opening of the stage, and 

 consist of plates with different sized apertures. A better form is 

 composed of one large disc containing several apertures of different 

 sizes. This is fastened to the under surface of the stage in such a 

 way that by revolving the disc the apertures may be brought one 

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