Mounting Of Specimens

USE OF JARS AND PLASTIC BAGS In the past, only thick-walled glass jars were used and these still can be recommended. They are inert to fixatives and aggressive mounting fluids such as oil of wintergreen (used for cleared specimens), which dissolves plastics. However, glass jars are heavy and not always available in the desired shape and size; they also break easily.

Currently, acrylic resins are the material of choice. Excellent optical properties, low weight, minimal breakability, and chemical stability to most mounting fluids are the outstanding characteristics of this material. Museum jars can be prepared in many sizes and shapes. The material is easy to cut, machine, and assemble. Fusion of the plates is accomplished with WELD^ON 4TM (IPS Corporation, Box 379, 17109 S. Main Street, Gardena, CA 90248). There are a few disadvantages. Plastics of this type are easily scratched and may have to be repolished on occasion. As stated, oil of wintergreen but also benzyl ben-zoate cannot be used as mounting fluid because they dissolve plastics. Instead of alcohol, which crazes the surface of plastic containers, mounting media with Prague solution should be used as described below.

An alternative to acrylic museum jars are plastic bags. They are suitable for many purposes because they are light, tough, inexpensive, and easy to prepare. Their pliability permits palpation of the specimen. The preservation fluid can be replaced repeatedly if cloudiness develops. Plastic bags are now used for teaching, examinations, and storage. Plastic bag materials and sealing procedures are described in Chapter 16.

MOUNTING MEDIA We fill our plastic museumjars with Prague solution: 128 g Prague powder*, 25 g erythorbic acid (L-ascorbic acid), 10,000 mL distilled water, 1,000 mL concentrated formalin, 4,000 mL solution A (see below), 4,000 mL solution B (see below).

*Milwaukee Seasonings, N113W18900 Carnegie Drive, Germantown, WI 53022.

Solution A: 47 g sodium phosphate (Na2HPO4), formalin solution, 10%, to make 5,000 mL.

Solution B: 45 g potassium phosphate (K2HPO4), formalin solution, 10%, to make 5,000 mL.

Solutions A and B must be stored in separate containers.

For mounting fluids used with grossly stained specimens, see Chapter 14.

PLASTINATION This method may replace many of the traditional museum techniques because one can not only mount the samples in the traditional manner but tissues also can be merely infiltrated (without mounting them) and then be palpated and viewed more directly than organs and tissues mounted in jars (5-7). We had much success with a commercially available material (8) (Plastination Biodurâ„¢ Products Program, Dr. von Hagens, Rathausstrasse 18, Heidelberg, Germany). Specimens such as aortas can be infiltrated and in many respects resemble the fresh tissue. Other samples such as slices of brain can be embedded in solid blocks. The materials used for the plastina-tion procedure vary, depending on the intended end product. Company directions must be followed closely.

MOUNTING IN SOLID PLASTIC If successful, embedding of specimens in solid blocks of plastic compounds yields excellent museum specimens. Materials are commercially available and may give satisfactory results (Wards Natural Science Establishment, Inc., P.O.Box 92912, 5100 West Henrietta Road, Rochester, NY, 14692-9012).

Unfortunately, the embedding techniques are complicated because the samples must be carefully dehydrated, a procedure that will distort most autopsy tissues. Cracks, incomplete hardening, or clouding of the polymer may occur, and specimens may shrink or become spongy. Artifacts may also be created by the heat of the exothermic polymerization of the monomer. Best results are usually achieved with specimens such as bullets, concrements, or casts. Again, the instructions of the suppliers must be followed closely, and one must heed the warnings as to the danger of explosions and the need to protect eyes and hands. Specimens embedded in solid blocks are difficult or impossible to retrieve for further study.

LABELS To identify and describe museum specimens, labels can be glued to the jar or inserted between an outer and an inner plastic bag. Labels on the outside of a container can accidentally be torn off; an identifying tag should always be attached to the actual specimen inside the jar or plastic bag. Identifying tags or labels enclosed with the specimen must be made of material capable of resisting the chemical action of the mounting fluid.

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Responses

  • Aryan
    Which fluid is used for mounting museum specimen?
    9 months ago

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