Il6 DEMONSTRATING BACTERIA IN TISSUES 



and place under a tap of running water. The water of 

 course, overflows, but the tissues remain in the bottle 

 (Fig. 71). 



4. Impregnate the tissues with mucilage for twelve 

 to twenty-four hours, according to size. Transfer the 

 pieces of tissue to a bottle containing sterilised gum 

 mixture. 



Formula. 



Gum arabic 5 grammes 



Saccharose i gramme 



Boric acid i gramme 



Water 100 c.c. 



5. Place the tissue on the plate of a freezing micro- 

 tome (Cathcart's is perhaps the best form), cover and 

 surround with fresh gum mixture ; freeze with ether, or 

 for preference, carbon dioxide, and cut sections. 



6. Float the sections off the knife into a glass dish 

 containing tepid water and allow them to remain 

 therein for about an hour to dissolve out the gum. 



(If not required at once, store in 90 per cent, alcohol.) 



7. Transfer to a glass capsule containing the selected 

 staining fluid, by means of a section lifter. 



8. Transfer the sections in turn to a capsule con- 

 taining absolute alcohol (to dehydrate) and to one 

 containing xylol or oil of cloves (to clear). 



9. Mount in xylol balsam. 



Alternative Rapid Method. 



1. Cut very small blocks of the tissue. 



2. Fix in formalin 10 per cent, aqueous solution (fixation fluid 

 No. 7, page 82) for 24 hours. 



3. Transfer block to plate of freezing microtome and freeze with 

 carbon dioxide vapour. 



4. Float the sections off the knife into a glass dish of tepid 

 water. 



5. Stain the sections in glass capsules containing selected stains. 



6. Place the stained section in a dish of clean water and 

 introduce a glass slide obliquely beneath the section; with a 

 mounted needle draw the section on to the slide and hold it there; 



