THE ESSENTIALS OF HISTOLOGY 



LESSON I. 



USE OF THE MICROSCOPE. EXAMINATION OF 

 COMMON OBJECTS. 



THE requisites for practical Histology 

 are a good compound microscope mag- 

 nifying from about 50 to 400 linear ; slips 

 of glass technically known as ' slides,' 

 upon which the preparations are made ; 

 small pieces of thin glass used as covers 

 for the preparations ; a few simple instru- 

 ments, such as a razor, a scalpel, scissors, 

 tine-pointed forceps, and needles mounted 

 in wooden handles ; and a set of fluid re- 

 agents for mounting and staining micro- 

 scopic preparations. 1 A sketch-book and 

 pencil are also requisite, and must be con- 

 stantly employed. 



Examine the microscope (fig. 2). It 

 consists of a tube (t t') having two systems 

 of lenses, one at the upper end termed 

 the ' eye-piece' or ' ocular ' (oc), the other, 

 at the lower end, termed the ' objective ' 

 (obj). There should be at least two 

 objectives a low power, working at about 

 i inch from the object, and a high power, 

 having a focal distance of about inch. 

 The focus is obtained by cautiously bring- 

 ing the tube and lenses down towards the 

 object by the coarse adjustment, which is 

 either a telescopic or a rack-and-pinion 

 movement (adj), and focussing exactly by 

 the fine adjustment, which is always a 

 finely cut screw (adj r ). 



The stage (st) upon which the prepa- 

 rations are placed for examination, the 

 mirror (m) which serves to reflect the light 

 up through the central aperture in the 

 stage and along the tube of the instrument, 

 and the diaphragm (d) below the stage 

 which serves to regulate the amount of 

 light thus thrown up, are all parts the 

 employment of which is readily under- 

 stood. 



It is convenient to begin the study of 

 FIG. 2. DIAGRAM OF MICROSCOPE, histology by the examination of the blood, 



' The directions for making the principal fluids used in histological work will 

 be found in the Appendix. 



