THE MICROTOMIST'S 

 VADE-MECUM 



PART I 



CHAPTER I 



INTRODUCTORY 



1. The General Method. The methods of modern microscopic 

 anatomy may be roughly classed as General and Special. There 

 is a General or Normal method which consists in carefully fixing 

 the structures to be examined, staining them with a nuclear 

 stain, dehydrating with alcohol, and mounting series of sections 

 of the structures in balsam. It is by this method that the work is 

 planned and very often finished. Special points are then studied, 

 if necessary, by Special Methods, such as examination of the 

 living tissue elements, in situ or in " indifferent " media ; fixation 

 with special fixing agents ; staining with special stains ; dissocia- 

 tion by teasing or maceration ; injection ; impregnation ; and 

 the like. 



There is a further distinction which may be made, and which may 

 help to simplify matters. The processes of the preparation of tissues 

 may be divided into two stages. Preliminary Preparation and Ulterior 

 Preparation. Now the processes of preliminary preparation are 

 essentially identical in all the methods, essential divergences being only 

 found in the details of ulterior preparation. By preliminary preparation 

 is meant that group of processes whose object it is to get the tissues 

 into a fit state for passing unharmed through all the ulterior processes 

 to which it may be desired to submit them. It comprehends the 

 operations of (1) killing ; (2) fixing ; (3) the washing and other mani- 

 pulations necessary for removing the fixing agent from the tissues, 

 and substituting for it the preservative liquid or other reagents which 

 it is desired to employ. Ulterior preparation comprehends the pro- 

 cesses sketched out in §§ 3 et seq. 



2. Preliminary Preparation. The first thing to be done with 

 any structure is to fix its histological elements. (This state- 

 ment applies equally to all classes of objects, whether it be desired 

 to cut them into sections or to treat them in any other special 

 way.) Two things are implied by the word " fixing " : first, 

 the rapid killing of the element, so that it may not have time 

 to change the form it had during life, but is fixed in death in 



VADE-MECUM. 1 1 



