BACTERIOLOGICAL TECHNIQUE 29 



(a) Exposure to a temperature of 110-115 C. in hot-air chamber 



for a few minutes. 

 (6) Immersion in absolute alcohol. 



(c) Immersion in equal parts of absolute alcohol and sulphuric 



ether for thirty minutes. 



(d) Immersion in a solution of formalin for five minutes. 



(e) According to Ehrliclv's method, on a metal plate, which 



is heated. 



The above methods of fixing are specially adapted for detecting 

 corpuscular changes, etc. For ordinary bacteria proceed 

 as at No. 4, general method, 8. 



6. To stain for bacteria, use the ordinary stains for that purpose. 

 The special stains for Malaria are described under 'Malaria' in 

 Part III. 



Precautions. In examining specimens of blood for bacteria an 

 excess of haemoglobin is liable to exist, which interferes with the 

 isolation of the organism. Remove the excess before fixing, by 

 placing the cover-glass specimen in a three per cent, solution of acetic 

 acid for a few seconds, wash with distilled water, dry, and proceed as 

 above at No. 4, general method, page 17. 



XXIX. METHOD OF REMOUNTING AND RESTAINING 

 COVER-GLASS SPECIMENS. 



1. Heat the slide in the flame of the Bunsen to warm the balsam ; 

 when it is melted remove the cover-glass, and transfer to another slide. 



2. To restain the cover-glass specimen, place it, after removal from 

 the slide, in xylol for twenty-four hours, which is changed several 

 times to ensure thorough removal of the balsam. 



3. The cover-glass is now placed in absolute alcohol to remove the 

 xylol, and stained according to the method desired. 



XXX. NECESSARY PRECAUTIONS IN MANIPULATING 

 COVER-GLASS SPECIMENS. 



1. Never handle a heated cover-glass with cold forceps, as it 

 generally breaks. 



2. All specimens must be thoroughly air-dried, otherwise the 

 albuminoids coagulate under the influence of heat. Some bacteria, 

 i.e., Bacillus anthracis, change their form, break up, are surrounded by 

 a halo, and lose their affinity for the stain. 



