Re: Zenker fixative

Jill Songer HT (ASCP), Supervisor, Anatomic Pathology, Veterinary Medicine 
Teaching Hospital, Virginia Tech (Jill, is that in Blacksburg VA?) asks:

>>Back in the old days, when Zenker's fixative was used, the slides had to 
treated with sodium thiosulfate, iodine, alcohols, etc to remove any pigment 
or precipitate formed by the mercuric chloride used. My question-is this step 
still required with Zenker's that has zinc instead of mercuric chloride?<<

Abraham Lincoln was fond of asking, how many legs does a dog have if you call 
a tail a leg. Our beloved 16th president would then explain that the answer 
is four, because the tail still isn't a leg whatever you call it.

Zenker's fixative (with acetic acid, strictly speaking) and Helly's fixative 
(with formaldehyde) contain mercuric chloride and potassium dichromate. The 
brown granular mercury precipitate must be removed from the sections with 
iodine. A zinc fixative doesn't require this step. But it isn't Zenker's 
fixative - no matter how many MBA's and marketing departments say it is - and 
cannot be substituted for it.

Bob Richmond
Samurai Pathologist
Knoxville TN

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