TECHNIC. 



§ I . Very few structures of the animal body can be examined 

 microscopically without being first subjected to a preparatory treat- 

 ment involving in most cases the employment of complicated meth- 

 ods. Increase in our knowledge of the finer structure of the body 

 in the past has been accompanied and made possible by the improve- 

 ments in the methods employed. Advance in the future, likewise, 

 will be dependent on the application of a more exact technic. For 

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

 mastery of the more important methods is indispensible ; for the 

 student of pathology, also, very desirable is the acquisition of skill 

 in the application of simple methods which require neither expensive 

 apparatus nor expenditure of time, — methods which, while they do 

 not advance knowledge, serve to meet the needs of a rapid clinical 

 diagnosis. 



Of the multitudinous methods employed in microscopic work, 

 only those are here given which are necessary for a general working 

 knowledge in histology, or are used in this course. Animal tissues 

 are bulky and unfitted for examination under high powers of the 

 microscope ; examination may be made possible in one of two 

 ways, — the elements composing the structure may be separated from 

 each other, or thin slices may be prepared. Furthermore, tissue 

 may be examined in either of these ways, fresh (or alive), or after 

 special chemical treatment. The technic of histology involves 

 then : 



A. Examining fresh, by either B. or C. Advantageous or neces- 



sary when haste is required, or in examining the tissue 

 alive. 



B. Isolation or Dissociation. Separating out the elements compos- 



ing a tissue by (a) teasing or (b) treatment with reagents 

 and teasing. 



C. Cutting thin sections of the tissue or organ. 



