24 PRACTICAL HISTOLOGY. 



one who is working with the microscope should be 

 without. 



Lastly, the student should never trust to the 

 transient impression of form or structure which the 

 mere glance at a microscopic preparation conveys, 

 but should always, whether naturally a good 

 draughtsman or not, endeavor to perpetuate the im- 

 pression so obtained by a careful sketch showing 

 the more important points which the preparation 

 illustrates. The rough outlines maybe drawn with 

 a camera lucida or drawing prism, if one be avail- 

 able, but even without such an instrument a little 

 practice soon enables a sketch to be produced which 

 gives a fairly good idea of the appearances seen, and 

 however rough it may be, serves materially to assist 

 the memory. 



For the most part it is also desirable to note the 

 results of measurements made with a micrometer. 

 The use of this, as well as the method of sketching 

 an object by aid of the camera lucida, will be 

 described in the Appendix at the end of the book. 



