INTRODUCTION

For thousands  of  years,  desiccation  of  biological tissue has been a useful and inexpensive  means  of specimen preservation (Kitchel et al., 1961; Strub and Frederick, 1 967; Church ,  1 968).  Plastination,  though well known for its unique preservation qualities of anatomical  specimens  (von Hagens  et  al.,  1987; Nicaise, 1 990; Weiglein, 1996; Latorre et al, 2001 , 2002) is still more costly than desiccation in many regions today . However, insects have a predilection for consuming organs dried in such a manner. A simple mechanism to prevent  infestation  of  desiccated  organs with insects thus preventing organ destruction  would serve to greatly increase the longevity and usefulness of desiccated  specimens.  This  study  will  describe  a mechanism of organ preservation  and protection .

MATERIALS AND METHODS

Hollow organs were collected  from  animal  cadavers for use in this study. The stomach , large colon and descending colon were harvested from a  horse. Stomachs,  lungs and  female  reproductive  tracts  were removed from a cow, sheep and dog. The organs were flushed with tap water until free of ingests . The adipose tissue, omenta and mesentery were removed close to the organ using caution not to damage the  outer  muscle layer. Once clean, the organ was prepared for classic air drying by cannulation of both ports  with  appropriate sized tubing and hooked to a laborato1y air source. The organ was first dilated to the desired degree of inflation . Air flow and hence organ size was either controlled by adjusting the inflow and/or the exhaust port by either occlusion or throttling by partial closure. Depending on the size of the organ,  drying  takes  three  to  four  days. The stomach (monogastric  and  ruminant) ,  small  and large intestines, lungs and uterus and vagina have been preserved  by  this  method.  The  second   phase commences after drying is completed and consists of gradual injection  of  the  plastic  expanding  foam, [Tekapur  (Bosnia-Hercegovina)  or  Great  Stuff  ( USA)]. It was beneficial to have an exhaust in addition to the inflow. If too much  loss of foam occurs via the exhaust, it can be decreased  in size or closed. The next day, more foam may be injected through one of the ports to fill areas that are devoid of foam to assure complete lining and filling of the organ. The hardening time is eight hours to one or two days depending on the volume of the organ.  Varnish was sprayed and brushed onto the external surface of the organs.  As well, region s of the organ or the entire organ may be painted.

RESULTS

Cleaning and  air drying the organs resulted in a desiccated  specimen   representative   of  those   occurring in situ. (Fig. I ) The surfaces of the  desiccated  organs were dry to the touch and free of any greasy residue. The injected  plastic expanded 2 to 4 times in volume in all directions and hardened gradually. Areas of the organs  which       par1ially  collapsed  following disconnection from the air  source  were  inflated  with the expanding foam . The  hardening time for the injected foam is eight hours  to  two  days  depending  on  the volume of the organ . The resulting dried, foam  filled organs were light weight and anatomically precise (Fig. 2). Application of the varnish to the outer surface of the organs was accomplished  without  the  production  of  a runny, streaked appearance. Paint was applied with a brush to highlight anatomical information (Fig. 3).

Figure I. Visceral view of canine air dried stomach . Cannula is in the esophagus.

Figure 2. Visceral view of foam filled canine airdried stomach. Note fat on minor curvature that must be trimmed off

Figure 3. Parietal view of foam filled, varnished and regionally painted equine air dried stomach.

DISCUSSION

A i r-drying of organs has been used for  anatomical applications  for  many  years (Mc Kiernan  and  Kneller,  1983; Henry,  1 992).  However,  filling air  dried  organs with expandable foam protects the otherwise vulnerable

inside of the  organ  from  insect  damage  while  the app l i cation  of varnish  does the  same for the external

surface.   The   foam   also   protects   the   organ    from collapsing under normal hand l i ng conditions. Various methods and products have been used to make a i r dried organs resistant to insect damage including fiberglass (Kitchel et a l. , 196 1 ), flexible plastic resin (Updike and Holladay, 1 986) and silicone (Henry and Butler,  1990). During filling it is beneficial to allow air to exhaust during inflation of organs. Continual flow of air through the  specimen  allows  the  organ  to  dry  quicker.  lf  the muscular wall of the organ is cut, a herniation or blow out of the mucosa may result from inflation without an exhaust port. If too much foam is lost through the exhaust port during injection , the portal may simply be closed. It is possible this expanding foam could also be used to dilate silicone impregnated hollow organs prior to polymerization  in the plastination  process.    It  is imperative  to  remove  all  adipose  tissue  from   the specimen prior to desiccation . The  failure  to  do  so results in greasy specimens to which the application of varnish  is  troublesome.  The  foam  products  tested  are unstable when exposed  to acetone. Acetone dissolves the foam and reduces it to a sticky  substance.  This would    preclude    the    use    of    the    foam    prior    to impregnation of specimens during plastination  during which step the acetone is removed from the specimen. Alcohol saturates the foam but does not dissolve it which opens the possibility of its use in plastination when alcohol i s the intermediary solvent. The external surface is protected from insect damage by varnishing. Once varnished, the external surface of the organ may also   be  painted   or    labeled   for   demonstration   of information . This method produces  specimens  that maintain  normal  anatomical  form,  are  durable  and inexpensive to produce.