47 



necessary to dehydrate by passing through successive 

 strengths of alcohol, as the shrinkage would be great 

 if the tissue were passed direct from water to absolute 

 alcohol. This may be effected in the following way : 

 To 9 c.c. of water containing the washed tissue add 

 I c.c. of absolute alcohol. The strength of alcohol 

 is now ten per cent. Leave for ten minutes. Take 

 out 5 c.c. and add I c.c. of alcohol, the strength is now 

 twenty-five per cent. Leave for ten minutes. Take 

 out 2 c.c. and replace by I c.c. of alcohol ; the strength 

 is now forty per cent. Leave for ten minutes. 

 Continue in this way to take out 2 c.c. and replace by 

 i c.c. of absolute alcohol. It will be seen that the 

 process takes an hour. If the tissue is not going to be 

 imbedded stop at eighty-five per cent. Otherwise at 

 this stage place in absolute alcohol ready for passing 

 through cedar wood oil. 



N.B. This process is only necessary where extreme care is to be 

 taken in the preservation of histological details, otherwise change 

 from the water to (about) eighty-five per cent, alcohol directly and 

 renew it once. 



TABLE FOR PASSING THROUGH INCREASING STRENGTHS 

 OF ALCOHOL 



9 c.c. H. 2 O + I c.c. 1 00% alcohol = 10 % alcohol. 



5 c.c. 10 % + i c.c. - 25 



4 c.c. 25 + i c.c. -- 40 



3 c.c. 40 + i c.c. = 55 



2 c.c. 55 + i c.c. - 70 



I c.c. 70 + i c.c. , ?> 85 



Any convenient multiple of these quantities may, 

 of course, be used. 



STAINS, ETC. 



i. Romanowsky Stains. Vide p. 21. The best 

 stain for parasites in the blood, etc. 



