How to preserve museum specimens (Museum mounting techniques)

All teaching hospitals and colleges of pathology have museums that serve many functions: permanent exhibition of common specimens for undergraduate and postgraduate teaching purposes such as collected animals, illustration of rare specimens, permanent source of histological material and for gross and microscopic photography.

Any museum specimens are handled by the following steps:

1. Reception
2. Preparation
3. Fixation
4. Restoration
5. Preservation
6. Presentation

Reception of the Specimen

Any specimen received in the museum should be recorded in a reception book and given a number followed by year( e.g. 32/2013). This number will remain with the specimen even after it is cataloged in its respective location.This number is written in indelible ink on the tie- on type label and is firmly attached or stitched to the specimen. The reception book should contain all necessary information on the specimen( clinical, gross and microscopic findings).

Preparation of the specimen

An ideal specimen is received fresh in unfixed condition.However, it is mainly obtained from the pathology laboratory after examination, so formalin is already fixed.If you plan to use a specimen for the museum, part of it can be kept without disturbing the museum, for example the kidney can be bisected and half kept aside for the museum.

Fixation of the specimen

The aim of fixation is to preserve cells and tissue constituents as closely as possible and to allow them to undergo further preparatory procedures without change. Fixation stops autolysis and bacterial decomposition and stabilizes the cellular and tissue components.The fixatives used in museums around the world are based on formalin fixation techniques and are derived from the Kaiserling technique and his modifications.Kaiserling recommended that the initial fixation be a neutral formalin( KI) solution and then transferred to the final preserving glycerin solution( KIII) for long- term display.Color preservation with these solutions is also maintained.

Kaiserling Technique of fixation

Fixation of specimen

The specimen must be kept in a large enough container that can accommodate specimens with a fixative volume of 3- 4 times. Specimen are stored in the Kaiserling I solution for 1 month, depending on the size of the specimen.The specimen should not rest at the bottom or an artificial flat surface is produced during hardening due to fixation.

Composition of Kaiserling I Solution

How to restore the specimen after fixation

It is necessary to restore the specimens as they lose their natural color on fixation. The method recommended is the Kaiserling II method. It involves removing the specimen, washing it in running water and transferring it to 95 percent alcohol for 10 minutes to 1 hour depending on the size of the specimen.The specimen is then kept and observed for about 1- 1.5 hours for color change. After this step, the specimen is ready for conservation.

Kaiserling II Solution

It contain 95% Alcohol.Store specimen in this solution for 10 minutes to 1 hour depending on size of specimen.

Rejuvenator Solution

* Formalin decreases the natural color of the specimen. However, the rejuvenator solution restores color.

How to preserve the specimen

Kaiserling III is the recommended solution for this step. This is the final solution in which the specimen will be displayed. It is based on a glycerin solution.

Composition of Kaiserling III Solution

Adding thymol crystals in order to prevent moulds.

* Leave solution to stand for 2 – 3 days before use to ensure proper chemical mixing

Add 1% pyridine as a stabilizer. This solution acts as a permanent fixation. This solution easily turns yellowish and needs to be replaced to restore the color of the specimen. The specimen will first float to the surface, but later sink to the bottom.

Presentation of the Specimen

Initially, all museum specimens were mounted in cylindrical jars and sealed with bladder sheep walls. they were later replaced by rectangular glass jars. They were better than cylindrical ones, as the flat surfaces offered a clear view of specimens without distortion.They are covered with rectangular glass plates.These jars can be purchased readymade or assembled in the museum itself, as needed.Perspex jars are now also available, which are lighter than glass jars.they can not, however, be used to store specimens fixed in alcohol or methyl salicylate as they react with plastics.

How are Specimens mounted in museums

It is attached to the specimen plate or rectangular bent glass rods to support the specimen within its jar. It can be done by attaching the specimen to nylon threads. Double knots should be made by threads on the surface of the specimen.

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