MICROSCOPIC STUDY AND STAINING 129 



When an intense stain is desired, the solution of eosin and azur 

 II may be flooded over the preparation together, using an excess 

 of azur II. They are then left on from five to ten minutes. At the 

 end of this time washing and drying as before complete the process. 



The Staining* of Bacteria in Tissues. The preparation of tissue 

 for bacterial staining is, in general, the same as that employed for 

 purposes of cellular studies, in histology. For bacteriological studies 

 the most useful are alcohol and Zenker's fluid. Other fixations, 

 such as that by formalin, or Mueller's fluid, give less satisfaction. 

 In other respects the details of dehydration and embedding are the 

 same as those used in histological studies, except that it is desirable 

 that the tissues should be handled rather more carefully than is 

 necessary for ordinary pathological work, and the changes from 

 the weaker to the stronger alcohols should be made less abruptly. 37 



Embedding in paraffin is preferable to celloidin, although the 

 latter method is not unsuccessful if carefully carried out. The chief 

 disadvantages of celloidin are the retention of color by the celloidin 

 itself and the consequent unclearness of differentiation. It is also 

 easier to cut thin sections from paraffin blocks than from those 

 prepared with celloidin. 



When staining tissue sections for bacteria, it is most convenient 

 to carry out the process with the section attached to a slide. For 

 celloidin sections this may be accomplished by means of ether vapor. 

 For paraffin sections it is necessary to cover the slide with an 

 extremely thin layer of a filtered mixture of equal quantities of 

 egg albumin and glycerin, to which a small crystal of camphor or 

 a drop or two of carbolic acid has been added. The sections are 

 then floated upon a slide so prepared, and set away in the thermostat 

 for four or five hours. 



LQEFFLER'S METHOD. 58 Stain in alcoholic methylene-blue solution five to 

 fifteen minutes, or in Loeffler's alkaline methylene-blue solution one to twenty- 

 four hours. 



Wash in one to one-thousand acetic acid solution for about ten seconds. 



Treat with absolute alcohol by pouring the alcohol over the preparation 

 for ten to twenty seconds. 



Clear with xylol. 



Mount in balsam. 



31 For details of such work reference should be had to the standard textbooks 

 on pathological technique, notably the very excellent one of Mallory and Wright. 

 **Loefiler } Mitt. a. d. kais. Gesundheitsamt, ii, 1884. 



