Fixing Sohiiions and their Uses 13 



color. Leave the tissue in this sokition from 5 to 8 hours, biu not longer. 

 If during this time the solution loses color, add some more iodine-alco- 

 hol. The iodine removes some, but probably not all, of the excess mer- 

 curic chloride precipitate left in the tissue. Later, when staining the 

 sections, iodine-alcohol or Lugol's solution (page 410) must be included 

 in the staining series. This should eliminate remaining crystals whic h 

 otherwise will persist as dark clinnps and needles in the finished slides. 



After Avashing, the tissue may be stored for several weeks or months 

 in 70% alcohol, but it is always safer to dehydrate and embed as soon 

 as possible. Storage in alcohol for long periods of time (a year or longer) 

 tends to reduce the stainability of tissues. This is also trtie after long 

 immersion in chromate and decalcifying solutions, or if traces of acid 

 or iodine are present. 



Do not use corked bottles for fixing or for alcoholic solutions; extrac- 

 tives from corks can be injurious to tissues. 



Fixing Solutions and their Uses 



Routine Fixatives and Fixing Procedures for 

 General Microanatomy 



bouin's fixative: 24 hours or longer — several weeks cause no damage. 



picric acid, saturated aqueous 75.0 ml. 



formalin 25.0 ml. 



glacial acetic acid 5.0 ml. 



Because of acetic acid content do not use for cytoplasmic inclusions. 

 Large vacuoles often form in tissues. Wash in 50% alcohol. The yellow- 

 color must disappear before staining sections. It usually is removed in 

 the alcohol series, but if not, treat slides in 70% alcohol plus a few 

 drops of saturated lithium carbonate until the color is extracted. 



BOUiN-DUBOSCQ (AlcohoUc Bouiu's) FIXATIVE (Pantin, 1946): 1-3 days. 



80% ethyl alcohol 150.0 ml. 



formalin 60.0 ml. 



glacial acetic acid 15.0 ml. 



picric acid crystals 1.0 gm. 



Prepare just before using. This is better than Bouin's for objects dif- 

 ficult to penetrate. Go directly to 95% alcohol. 



