THE PARAFFIN METHOD 129 



REMOVAL OF THE PARAFFIN 



To remove the paraffin, place the shde in a Stender dish of xylol. 

 About 5 minutes will be sufficient for sections 10 ii thick, but 10 or 20 

 minutes will do no harm. While a gentle heating will hasten the 

 process and will do no harm, you should never heat the slide e7iough to 

 melt the paraffin. Never attempt to warm the paraffin over a lamp. Over- 

 heating is ruinous. 



REMOVAL OF XYLOL OR TURPENTINE 



To remove the xylol, place the slide in equal parts of xylol and abso- 

 lute alcohol in a Stender dish. After 5 minutes, transfer to absolute 

 alcohol, which should also be allowed to act for 5 minutes. A little of 

 the paraffin will unavoidably be carried into the xylol-alcohol ; a 

 smaller quantity may be carried into the absolute alcohol. The ar- 

 rangement shown in Figure 15 will completely remove the paraffin 



before staining, 



TRANSFER TO THE STAIN 



After the paraffin has been removed with xylol or turpentine, and 

 the xylol or turpentine has been rinsed off with alcohol, the next step 

 is the staining. If the stain is a strong alcoholic one (85-100 per cent 

 alcohol), transfer directly to the stain. If the stain is in 70 per cent 

 alcohol, pass through 95 and 85 per cent alcohol, 5 minutes in each, 

 before staining. If an aqueous stain is to be used, pass down the whole 

 series — 95, 85, 70, 50, 35, and water — 5 minutes in each, before placing 

 the slide in the stain. 



This is rather tedious, but, for cytological work, it seems to be 

 necessary, and one might as well learn early that rapid work and good 

 preparations seldom go together. 



DEHYDRATING 



After the sections have been stained, they must be dehydrated. If 

 they have been stained in a strong alcoholic solution, transfer to 95 

 and then to 100 per cent alcohol, 2 minutes in each, if the stain does 

 not wash out too rapidly. If stained in an aqueous solution, pass 

 through the series — water, 5, 10, 20, 35, 50, 70, 85, 95, and 100 per 

 cent alcohol — about 2 minutes in each. 



With stains which wash out rapidly, the times must be shortened 

 and some of the alcohols must be omitted. With aqueous gentian vio- 

 let, all must be omitted except the 95 and 100 per cent, and even in 

 these the time must be shortened to a few seconds. 



