Pascal’s Flaw & the Rascal’s Law as applied to Embalming
Pascal’s Flaw & the Rascal’s Law as applied to Embalming
As requested, this information is intended to be provided to the embalmer who wishes to better understand how Pascal’s Law applies to what we do as specialist operating technicians. So to credit, we must honor and respect the prerequisite knowledge so freely available offered by French mathematician Blaise Pascal. In no way is the title intended to disrespect or dishonor any of his work, but instead to give the honor back to him by way of fully understanding his concept.
After deep consideration about how we might reach the largest portion of professionals, we decided upon an example we feel is most relatable but still easy to understand. We are going to talk about the drum brake hydraulic system inside motor vehicles. Before you decide this article is not for you, please respect the hydraulic system in a motor vehicle is as much a science as is what we do in the embalming room. That in matters of science, which is the eternal quest to truth, our theories, concepts and conclusions must apply universally to all science, and we must always be ready to resign our assumptions for truth.
The hydraulic system of a motor vehicle in theory is very complicated. When we look at it as a large portion it can be overwhelming. Don't be overwhelmed, we are going to take it one piece at a time and we promise it won't cost you a dime! If you got that joke, you might have grown up around old cars. So this might be a bit easier on you. For any younger professionals, don't worry, we have pictures! Believe it or not, the drum brake hydraulic system actually starts with your foot. You apply force (pressure that is, or energy) with your foot to depress the pedal. While you do this, the pedal slides a rod through the master cylinder. The master cylinder is a chamber which contains brake fluid, a viscous incompressible fluid. As the rod moves through the master cylinder, fluid is displaced. While fluid has no ability to escape, the force in which is being applied by your foot is now evenly distributed throughout the brake line system. Fluid sends the message of force, or energy. The brake line system is attached to the master cylinder and connects to each of the four wheel cylinders. The brake line system often contains a proportioning block to manipulate the distribution of force to the wheels. It manages to do this, believe it or not, much like the cannula or valves (yes; this does include your rate of flow valve) on the embalming machine. We will return to this point later on. For example, the proportioning block might keep a driver safer by distributing more force to the front of the vehicle rather than the back. An example that manipulation to Pascal’s law is within our control. As fluid enters the wheel cylinder and carries the message of force, a lever now pushes the brake shoes into the wheel drum which otherwise spin freely. The result is that the car comes to a stop. Let’s break it down for those who follow physics. First, force creates flow. Next, flow no longer has space to go. Last, the fluid carries the message of the force being applied in accordance with Pascal's law.
Now before we accept this as truth in what we do as embalming technicians, we must make a strong enough case that the human vascular system is enough like that of the hydraulic system described above. That fact is, at least from a scientific standpoint, that the human vascular system is vastly different from that of a hydraulic plumbing system. The most significant detail might be that the vessels of the human body are also meant to pass fluid from its space. It also is designed in such a way as to promote the distribution of oxygen rich blood to the tissues of the body by the pulse of the human heart. Detailed examination of the capillaries support the passage of fluid from artery to vein is done through a venturi. A venturi is a narrowed opening. While fluid moves through a venturi, it passes moving faster. For those that are following from a physics standpoint, higher pressure is held within the arteries, and lower pressure as fluid is returned via the venous system. We won’t totally discredit the application of Pascal’s law to what we do as embalmers. Surely, it has its place in science for a reason. There are certainly enough similarities between the vascular system and a drum brake hydraulic system to give us a more thorough understanding.
Please consider our aforementioned brake system once again. This time, imagine that someone has managed to cut the brake line near one of the wheel cylinders. How will this affect the driver’s ability to stop? Once again the driver will depress the pedal, displacing fluid from the master cylinder into the lines. But this time, rather than filling the space and sending a message of force, the fluid will continue to travel. This is because force is energy. The fluid will continue to travel in the path of least resistance, which would be out of the brake line. Fluid will not carry the message of force necessary to activate the brake shoes into the wheel drums and stop the car. The resistance fluid finds in its escape would be the only amount of force applied to the other wheel cylinders. Unfortunately for the driver, the force required to stop the vehicle is only generated if the fluid is unable to escape. Since fluid can freely escape, as the driver depresses the pedal, fluid continues traveling out of the brake line. This is a very dangerous situation for the driver. What is important to understand from a physics standpoint is that the larger proportion of energy applied stays in motion and travels with the fluid leaving. Not to mention, gravity will amplify the escape of fluid. So we now have a hydraulic brake system designed using Pascal’s law which has been disrupted by a rascal. Is it fair to say that a pressure system having an incalculable number of points of relief will disproportionately distribute force within its space according to what we will call the Rascal’s law? What would you call a vessel with an incalculable number of points of relief? An artery.
Illustration by A.Todaro, Inc. 2020 ©
Ultimately, it doesn’t matter what we call it. What is most important is that we understand it; that we prioritize data surrounding this. I would implore any well-meaning person or persons who have misspoke about this topic to edify their remarks. That any who put their strong beliefs, opinions or ego first over science choose to no longer proceed. A misrepresentation of this information is damaging an already crippled industry that will no longer exist or be relevant at the current trajectory.
Before we proceed into the complex situation of applying this information to the vessels of the human body, we will offer another hydraulic example involving relief. Imagine a pipe as tall as a tower starting from the ground. At the very top of this pipe which touches the clouds is a pressure gauge. This pressure gauge provides a measurement of force when force is applied to the bottom of the gauge, as most pressure gauges do. At the midpoint of the pipe is a tee fitting which is open, allowing fluid to escape. Now imagine you begin filling this pipe with a garden hose. Suppose how the pressure gauge would or would not be affected by this scenario. Using your same imaginary flow rate, suppose you plugged the midway tee fitting. How would pressure be affected when fluid fills the space and becomes still? Pressure would always be higher in the second circumstance, according to Bernoulli’s principle related to fluid dynamics. Elevation would substantially influence the distribution of force throughout our pipe while under conditions of relief.
So having already covered the necessary prerequisite knowledge of the the hydraulic drum brake system and the significant differences of the vascular system, we can begin to formulate some understanding of what occurs as embalming fluid is introduced into the human body. Pressure filtration is defined as the positive pressure within the artery, which results in the movement of fluid into the tissue that is then relieved by the venous system. While this concept may seem simple, each component—artery, vein, tissue—presents their own conditions which are relevant to our full understanding. While alive, the artery contracts and expands, and contains capillaries, which again are narrow openings encouraging the passage of fluid through venturis, which relieve fluid from this space. Next, we have tissue, which becomes saturated, desaturated or both as fluid passes through the vessels of the body. Last, we have veins, which accept fluid to be returned back towards the heart with valves that assist this process most notably located in the legs. So as fluid is introduced into the arterial system, at the same time it is being relieved. In accordance with our Rascal's law, this is a problem for embalmers to express uniform distribution of force to fluid in order to evenly saturate the human body. Honest experienced and inexperienced embalmers are aware of what disproportionate saturation of the tissues of the body can look like after embalming. In cases where this occurs, often the embalmer will raise a vessel nearest to the area with the greatest disparity to correct the issue and achieve proper saturation. Why can’t an embalmer enforce Pascal’s law within the arterial system? That answer is simple, if we have processed the information given beforehand, and realized that there are various degrees of resistance for fluid to pass throughout the entire system. The force which creates the flow will always pass fluid, taking with it most energy through the paths of least resistance. It should also be said that the force will be least applied to areas that present the greatest resistance. Now, there might be a few embalmers reading this who believe they’ve managed to outsmart this problem when they restrict drainage. But that is hardly a step toward cracking the Da Vinci Code. In fact, it is a regression and a misunderstanding of the components within the equation. Although we may be starting to equalize resistance within the venous system, how have we managed to prevent fluid from still taking the path of least resistance? Equalizing resistance within the venous system does not change the resistance needed for fluid to travel into the tissue. As embalming fluid interacts with the tissue of the body and water leaves the tissue, it does usually increase the resistance, but it does not mean that the path will provide enough resistance to force flow in another direction. It can help; however, it is an important detail to note that the venous system can be filled almost completely while drainage is restricted, while still only traveling fluid a short distance in the arterial system. As fluid pressure builds within the vessels of the body or as fluid meets resistance, fluid carries the message of force. When this force rises high, swelling or oversaturation of tissue occurs. Smaller arteries, having less strength, will burst before larger arteries and can present another point of relief either directly into the tissue, causing swelling, or out of the body, discouraging filtration of tissue. So rather than increasing the resistance in order to encourage fluid distribution, is it not a safer, wiser, more intelligent approach to remove resistance in some cases? When the speed of drainage increases, the ability of the embalmer to remove clots, pooled blood and obstructions also increases. This also is hardly a discovery for science. The Venturi effect is a well-known principle of fluid dynamics credited to Daniel Bernouli. While backpressure can be responsible for pushing clots and pooled blood during sectional embalming, during single point injections a vacuum force is generated as fluid escapes. As the speed of drainage increases, the vacuum force to pull fluid from other vessels increases as well. The result of copious or thorough drainage is a reduced general pressure demand as clots, pooled blood and obstructions are eliminated.
It is to the benefit of the embalmer to fully understand the concepts of pressure, flow, and relief to manipulate the disproportionate saturation of the body during arterial embalming. An embalmer makes an informed decision of which chemicals to preserve and disinfect. Can they not also choose the most appropriate injection and drainage site to promote the most satisfactory result? And so, it is to the benefit of the embalmer to both understand the physical sciences explained, and how to impart this knowledge as conditions in which they introduce fluid within the human body. There are various devices available to the embalmer to introduce fluid within the vessels of the human body. None of which should be regarded as insufficient so much as the centrifugal pump embalming machines, which manipulate pump force and flow by relief back to the tank. This condition of fluid travel, not only invalidates the measurement of pressure on the embalming machine, but also offers a path of lesser resistance against adversity within the body. This in turn increases the number of cases having large disproportionate saturation and multipoint injections. On the contrary, the hand pump itself, though simple, offers no relief and is a great advantage to an embalmer trying to saturate a poorly saturated area, avoiding an otherwise troubling, time-consuming process. Try it sometime and see for yourself.
Sadly, the embalming profession has truly lost its way. Not to hold embalmers in a higher regard than the mechanics or the engineers responsible for the hydraulic drum brake system—but they surely learned quite quickly being responsible for whether a driver would be able to stop the motor vehicle or not. Do the sentiments of life and death, as well as the sciences, not equally apply to us? Life or death situations are the circumstances that can make or break. Unfortunately, the business of high presentation and representation with bold claims of incredible value has held itself in such high regard that it has ignored other industries of science. This decision has consequences, and the consequence is that it has fallen far behind advancement. It is to the point where Big Business will boast that they have “the best for fifty years,” while changing nothing but a casement of their product. To the point where they will announce the release of this same product incepted over fifty years ago, with nothing more but new aesthetically appealing flare. To the point that a family may choose to arrange the direct disposal of someone they love out of fear, having been witness to what a funeral home calls embalming. Shame on you, funeral service. This article is not about the art—it’s about the science, and what it means to fail. When you fail in science, it requires that you be honest, responsible, and take action using the data that is presented before you.
J. M. Bernaudo
An honest practicing licensed embalmer
Long Island, NY
Speed control syringe embalming pump
Speed control centrifugal embalming pump
Chief Research & Design Scientist
Your Mortuary Magic Store, Inc.
Illustration credit, peer review and editing by A.Todaro