INTRODUCTION. 



Very few structures of the animal organism can be adequately 

 examined microscopically without being first subjected to a prepara- 

 tory treatment involving in many cases the employment of compli- 

 cated methods. Save in the case of the body fluids and certain 

 membranes, animal tissues are bulky, more or less opaque, and 

 therefore unsuited for examination under the microscope which 

 requires surface or thin layers of substance. Examination is made 

 possible in such cases in one of two ways, the elements composing 

 the structure may be separated from each other, or thin slices may be 

 prepared. 



The above, however, presents but the grosser aspect of the neces- 

 sity of preparation of animal tissues for examination with the micro- 

 scope. The histological analysis of bodily structure makes further 

 demands on the refinement of methods. Treatment with chemicals 

 and stains (Fixation and Staining) has for its purpose not only the 

 preservation and delineation of structure, but its identification by 

 means of more or less definite chemical (physical) reactions. The 

 goal from this side of histological technique is an analysis from the 

 chemico-physical as well as the morphological aspect and the inter- 

 pretation of morphology in terms of physiology. Increase in our 

 knowledge of the finer structure of the body in the past has been, as 

 advance in the future will be, accompanied by and dependent on the 

 application of a more exact technique along these lines; while for 

 those who aim to do practical work in histology and pathology a 

 mastery of the more important methods is indispensable. 



Furthermore, in working with chemically altered structure 

 there is always the danger of losing sight of the conditions existent 

 in the living protoplasm. It is well, therefore, in addition to study 

 structure in the living or fresh state, as little altered from the natural 

 as may be. There is also very desirable the acquisition of skill in 

 the application of simple methods which require neither expensive 

 apparatus nor expenditure of time, methods which while they 

 may not advance knowledge, serve often to meet the needs of a 

 preliminary examination or rapid clinical diagnosis. 



Of the multitudinous methods employed in microscopic work 

 only those are here given which meet the requirements for a general 

 working knowledge in histology. In special investigations, it is 



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