INFILTRATION WITH PARAFFIN. 



changed into stronger spirit and so on until absolute 

 alcohol is reached. The slower this process is carried 

 out the better will be the results ; in practice the 

 strengths of the successive lots of spirit used may be 

 40 per cent., 75 per cent., and the strong methylated 

 spirit, and the block may remain in each for twelve 

 hours. Lastly, it goes into two successive lots of 

 absolute alcohol. 



In all cases the amount of fluid must be greatly in 

 excess. It is useless merely to cover the block with the 

 spirit. 



CLARIFICATION. 



In the next step the alcohol is removed from the 

 tissue and replaced by some fluid which will dissolve 

 paraffin. Fats are dissolved out from the tissues at 

 this stage. 



This step is also very simple. The blocks are passed 

 directly from absolute alcohol into chloroform and 

 allowed to remain there until they appear translucent. 

 It is not necessary to use a preliminary bath of a 

 mixture of alcohol and chloroform. 



It is a good plan to place the bottle containing the 

 block in a warm place with the cork out for an hour or 

 so before proceeding further, as by so doing the last 

 traces of the alcohol will be removed. 



INFILTRATION WITH PARAFFIN. 



This is the stage which presents most difficulties to 

 the home-worker, for it is necessary to keep the block 



