Rigor Mortis and Its Effect on Embalming

This month's tip on Rigor Mortis comes to us courtesy of Denver Mason, trade embalmer with Snyder's Embalming Service.  Thanks, Denver!

It is important to understand that different tissues take up embalming fluids at different rates of speed. The viscera, muscle, skin and arterial walls, in that order, have the greatest uptake of fluid.  Rigor mortis affects the amount of aldehyde taken up by the tissue.  During rigor mortis, the tissue may not appear to absorb very much of the injected solution. Sometimes it can be almost impossible to inject very much solution without causing swelling, especially when high pressures are used, and here is why.

The blood vessels are contracted like other muscular tissues, so their diameters are reduced in size. This obstructs the flow of the embalming fluid.  For this reason, the tissue is not in its best condition to receive the fluids.  It stands to reason that the ideal time to embalm would either be before or after rigor.

Breaking rigor by flexing the body has the effect of increasing the amount of preservative that the tissue will take up.  This is due to a breakdown of protein that results from the process of flexing the muscles.  As the proteins break down into simpler units, each unit will take up additional amounts of the preservative.  If rigor is allowed to pass without flexing the body, the tissue will have increased after the injection of fluid.  This, again, is due to the normal breakdown of protein structures so that more groups are available to take up the preservative.  At times, the embalmer is not aware that rigor has begun to develop when starting to inject the embalming solution.  Sometimes, the injected fluid has the effect of producing a "shock" when it starts to contact the tissue.  As a result, this appears to accelerate the onset of the rigor mortis. 

Because of this, what the embalmer thinks is firmness due to the chemical reaction of the injected fluid is really due to the rigor mortis.  If he has injected two or two and a half gallons of fluid, by the time he has noticed this state of "firmness" he probably figures the body is embalmed and stops injecting.  A few hours later, he will probably find that the embalmed body is no longer as firm as it was when it was first embalmed.   Eventually, the body may even become soft.