CHAPTER II 

 GENERAL STATEMENT OF METHODS 



Each of the reagents which has been prepared is used for one 

 or more of the purposes to be discussed in this chapter. 



All methods of preparation in microscopy are to enable us to 

 learn more of the structure and functions of objects than would 

 otherwise be apparent. We endeavor to study them in as near 

 their natural condition as possible. While the study of living or 

 of fresh material is desirable it can be carried on only to a very 

 limited extent. Most structures of the animal body, though 

 opaque, must be examined largely by transmitted light, hence, 

 special preparation is necessary to put them into suitable condition. 

 This is accomplished 



1. By cutting them into thin slices (section method}. 



2. By separating them into their elements (isolation) 



) Mechanically (teasing}, or 



&) With the aid of fluids which remove the cement sub- 

 stance (dissociation or maceration}. 



In most instances, the minute structure of a tissue or of an 

 organism can be studied to the best advantage only after the appli- 

 cation of certain agents which serve to emphasize the various struc- 

 tural elements. A tissue so prepared is an artificial product in 

 that it is not exactly the same as it was in the living organism, but 

 recent studies of protoplasm in the living condition by competent 

 investigators strengthen the belief that many reagents preserve 

 very faithfully the actual structure of the cell contents. The 

 liquid albuminoids are apparently the materials which suffer the 

 greatest modifications. Since alterations do occur, however, it is 

 clear that in our interpretations of prepared material we must 

 reckon carefully with both the original nature of the object and 

 with the factors introduced by ourselves. 



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