THE ESSENTIALS OF HISTOLOGY. 



LESSON I. 



USE OF THE MICROSCOPE. EXAMINATION OF 

 COMMON OBJECTS. 



THE requisites for practical Histology 

 are a good compound microscope ; slips 

 of glass technically known as 'slides,' 

 upon which the preparations are made ; 

 small pieces of thin glass used as coA^ers 

 for the preparations ; a few simple instru- 

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

 fine-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 necessary, and must be 

 constantly employed. 



Examine the microscope (fig. 5). 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 

 ^ inch from the object, and a high power, 

 having a focal distance of about ^ inch ; 

 and it is also useful to have two or more 

 oculars of different power. The focus is 

 obtained by cautiously bringing 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'), 



The stage (si) 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 is used to regulate the amount of 

 light thus thrown up, are all parts the 

 employment of which is readily under- 

 stood. A subetage condenser (not shown 



EIG. 5. DIAGRAM OP MICROSCOPE. 



1 The directions for making the principal fluids used in histological work will be found 

 in the Appendix. 



