CHAPTER III 



THE PREPARATION OF TISSUES AND ORGANISMS FOR 

 STAINING AND MOUNTING STAINING AND STAINING 

 METHODS 



A SELECTED few of the numerous methods devised for 

 the preparation and staining of tissues, bacteria, etc., are 

 here given. Special methods occasionally employed will 

 be described when required. 



Preparation of Tissues 



In bacteriological work the demonstration of the 

 bacteria in the tissues is the primary object, and, there- 

 fore, the elaborate methods which have been devised for 

 fixing the tissue elements are not usually required unless 

 the minuter changes in the latter are being studied. The 

 tissues should always be obtained as fresh as possible, 

 because within a few hours of death they are invaded 

 by numerous bacteria, derived from the air and from the 

 intestine, which may mask the original bacterial infection 

 and lead to serious mistakes unless this source of error 

 be carefully borne in mind. In all cases the tissue should 

 be cut into pieces of convenient size, not more than about 

 1 cm. in thickness, and organs if kept en masse, should be 

 sliced. Having been thus prepared, the material may 

 be treated by one of the following methods : 



(a) Place directly in alcohol 1 for a week or a fortnight. 



1 Methylated spirit may usually be employed for all purposes when an 

 alcohol of not more than 90 per cent, strength suffices. It must, however, 

 be free from mineral naphtha, which is present in all " shop " methylated 

 spirit. Methylated spirit free from mineral naphtha can be obtained in 



