3t> ESSENTIALS OF BACTERIOLOGY. 



Cutting. The microtome should be able to cut sections 

 inch in thickness ; this is the fineness usually required. 



The sections are brought into alcohol as soon as cut unless 

 they have been imbedded in paraffine, when they are first washed 

 in chloroform to dissolve out the paraffine. 



Staining. All the various solutions should be in readiness, 

 best placed in the little dishes in the order in which they are to 

 be used, as a short delay in one of the steps may spoil the speci- 

 men. 



A very useful instrument for transferring the delicate sections 

 from one solution to another is a little metal spatula, the blade 

 being flexible. 



A still better plan, especially when the tissue is "crumbling," 

 is to "carry out" the whole procedure on the glass-side. 



General Principles. The section is transferred from the alco- 

 hol in which it has been kept into water, which removes the 

 excess of alcohol, from here into 



Dish I, containing the stain; where it remains 5 to 15 minutes. 

 Then- 



Dith II, containing 5 per cent, acetic acid (1 to 20) ; where it 

 remains to 1 min. The acid removes the excess of stain. 



Dish III, water to rinse off the acid. The section can now be 

 placed under the microscope covered with cover-glass to see if 

 the intensity of the stain is sufficient or too great. A second 

 section is then taken, avoiding the errors, if any ; and having 

 reached this stage proceeded Avith as follows : 



Dish IV, alcohol, 2 to 3 seconds to remove the water in the 

 tissue. 



V. A few drops of oil of clores, just long enough to clear the 

 specimen to make it transparent (so that an object placed under- 

 neath will shine through). 



VI. Remove excess with filter-paper. 



VII. Mount in Canada balsam. 



