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Did you know that...

mechanical models of muscle contraction were fleshed out starting as early as the 17th century through the field of Iatrophysics?

Over one hundred children were intentionally exposed to lead without explicit consent in the Baltimore Lead Paint Study?

Iatrophysics

A page from Giovanni Borelli's De Motu Animalium, showing how various simple machines can be used to model different limbs

Iatrophysics or iatromechanics (fr. Greek) is the application of physics to medicine. It was a school of medicine in the seventeenth century which attempted to explain physiological phenomena in mechanical terms. Believers of iatromechanics thought that physiological phenomena of the human body followed the laws of physics. It was related to iatrochemistry in studying the human body in a systematic manner based on observations from the natural world though it had more emphasis on mathematical models rather than chemical processes.

Subfields

Iatrophysicists drew inspiration from various established physical phenomena in order to explain how certain biological processes took place and how this can be applied towards medicine.

Mechanics

Machines were used as models by Iatrophysicists to quantitatively describe linear and rotational motion of various biological systems such as human limbs and animals. Some models came into existence before Isaac Newton's formulation of his three laws in classical mechanics, drawing on basic principles of statics and dynamics to represent how a biological system behaved. Borelli was prolific in applying mechanics to a wide variety of humans and animals in different degrees of activity, drawing upon an array of simple machines and models for translational and rotational motion and equilibrium.

Fluids

Iatrophysicists were also interested in studying how bodily liquids and gases were processed. They sought to understand how blood circulated throughout the body and what effects it made on the body. System consisted of arteries, veins, and vasculature verified through experiment and microscope by Malphigi's observations of capillaries in animal lung tissue. Albrecht von Haller, as did Borelli, postulated that friction from the blood on vessel walls lead to body heat and even fever. A hydraulic model for motion by Rene Descartes implied the body had a system that maintained flow between the brain and muscles in equilibrium state through nerves and blood vessels.

History

Starting in the 17th century, quantitative fields such as physics and mathematics began gaining legitimacy as a means of studying the natural world with the advent of theory, practices, and instruments. Static principles and simple machines were already in use. The arrival of the microscope changed how natural philosophers thought about how to treat the human body.

Early Iatrophysicists

One prominent iatrophysicist was Giovanni Borelli, who modeled the human body, various animals, and their motions using mechanical principles. A colleague of Marcello Malphigi, Borelli was a mathematician who made connections between what he observed in living things and inanimate but relatively simple systems. He dissected animals and examined how muscles were to increase mechanical advantage, observed how a variety of living things performed different movements and activities such as running, carrying loads, swimming, and flying naturally rather than by his intervention, and devised simple methods to calculate a person's center of mass. He also devised relatively simple experiments and devices to make his observations such as a plank and rod for center of mass and a spirometer for volume of air [iatrophysics to biomechanics]. At the end of his life, his work culminated in De Motu Animalium (1679), a publication showcasing his investigations in similarities and differences in muscles across living things and his understanding of the underlying mechanism of muscle contraction, expansion via influx of fluids or gases released from nerves. He also attempted to describe more complicated processes such as nerve transmission and digestion.

Another notable iatrophysicist was the French philosopher and mathematician Rene Descartes, who, as a consequence of his philosophy asserting that the human body and soul are two dual entities, treated the human body as a machine that could be quantified, disassembled, and studied. He attempted to model various phenomena such as the brain, movement, sleep, circulation, and senses with analogies to inanimate objects such as reservoirs, pipes, lenses and steam engines that often sought to maintain an equilibrium for certain states. Some of his claims often were independent of physical observation of the organ or body in question and emphasized what he deemed as "simple" or "rational" rather than reality. For example, he asserts that blood circulates throughout the body by expanding as vapor by the heart's heat rather than from contraction.

William Harvey postulated blood flow as a closed, continuous loop that run throughout body that contained a certain quantity of blood. To test his claim, Harvey dissected human corpses and animals and, based on his anatomical findings, devised a simple demonstration of how arteries and veins continuously carried blood throughout the body. Taking advantage of the fact that arteries and veins were at different depths below the skin, he tied a person's arm and had them squeeze a bar to shunt blood from arteries to veins, indicating that blood somehow traveled along arteries and into veins. His claim was elucidated by Malphigi's discovery of capillaries and how they were interconnected with arteries and veins.

Other Iatrophysicists

Sanctorio Sanctorio (Santorius) (1561-1636) investigated human digestion with meticulous measurements over a long period of time. To study the mathematical relationship between food intake and excretions, Santorius developed a system with a chair and balance to find his net change in weight on a daily basis. He also analyzed the contents of his excretions and secretions, categorizing it by type and origin. He also made other instruments such as a clinical thermometer and pulse-clock.

Niels Stensen (Steno) (1638-1686) developed a mechanical and geometrical model of muscle movement, treating a muscle as a bundle of long, inter-connected fibers arranged in simple, uniform geometric shapes and changed their angles when contracting, thus modifying their shape at a fixed volume to either shorten or relax. This explanation of contraction, and his consequent theory that the heart contracted by shortening its fibers, was a radical departure from the popular theory that muscle fibers inflated themselves which was supported by well known Iatrophysicists such as Descartes and Borelli.

References

• Porter, R. (1997). The Greatest Benefit to Mankind: A Medical History of Humanity from Antiquity to the Present. Harper Collins. pp. p.227–228. ISBN 0-00-215173-1.

Baltimore Lead Paint Study

The Baltimore Lead Paint Study was a controversial clinical study conducted by the Johns Hopkins Kennedy Krieger Institute (KKI) in poor Baltimorean neighborhoods during the 1990s. The purpose of the study was to investigate the health effects of lead paint in children and the effectiveness of lower cost techniques in abating lead content in residential properties. Upon discovery of the study, the study ended at the turn of the millennia and met extensive criticism for issues regarding the target population, a significant portion of which were African American children, and patient ethics such as consent regarding children and health risks when exposing subjects to cheaper but less effective health conditions. The backlash culminated in class action lawsuits against KKI by Ericka Grimes and Myron Higgins, two of the subjects representing on the order of a hundred affected children without adequate care.

Background

Lead has a long history of being used in paint up until recently due to its role in maintaining a paint’s color and increasing durability. Lead’s toxicity was established as a valid concern to actively address in light of medicine’s development in the early half of the 20^th century. In 1951, Baltimore was the first city to ban the use of lead paint in new housing, starting a move towards abating the amount of lead use at home. 27 years later, in 1978 the Consumer Product Safety Commission laid down a nation-wide ban of lead paint in the United States.

The Kennedy Krieger Institute is a branch of Johns Hopkins that provides medical care, rehabilitation, and research, especially emphasizing research geared towards children with learning and physical disabilities arising from neurodegenerative disorders. Lead’s effects on the nervous system manifests into reduced cognitive ability, especially in children. Once lead paint was made illegal, many properties that were painted with lead still remained, especially in Baltimore, eventually leaving the painted walls that were not properly remodeled to decay and thus allow lead to be released as chips or dust, increasing risk of ingestion for future renovators and inhabitants. Thus it became of interest to study how residential properties with lead could be removed, and inevitably how to abate lead without incurring high expenses for removal.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1508654/pdf/amjph00006-0020.pdf       

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1733843/pdf/v030p00176.pdf

The experiment

To investigate how well various techniques in reducing lead content abated the prevalence of lead poisoning in low income neighborhoods, KKI sought to treat properties with these different methods and observe how much lead accumulated in young children when living in these properties. In total, properties were categorized into five levels. Starting in 1993, KKI helped landlords abate apartments partially or with less expensive techniques. In total, 107 properties were categorized into five groups by degree of repair made to the property. KKI also actively found new families to live in these apartments, bringing the total number of children evaluated to 140, and even offered incentives for doing so. To quantify the effectiveness of each level of abatement, the researchers measured lead content of homes and took periodic blood tests over a two year period. If the repairs were effective, the lead concentration in properties with higher degrees of abatement or built without lead would be less than properties with less repair and the lead content in young children would not increase. Follow up measurements would be made every couple of years.

https://www.epa.gov/sites/production/files/documents/r95-012.pdf

http://journalofethics.ama-assn.org/2003/11/hlaw1-0311.html

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1733843/pdf/v030p00176.pdf

Aftermath

Many children with neurological disabilities as a result, often incurring permanent nervous damage and thus the study was not beneficial for the children themselves in terms of their interests in health. Parents felt deceived by KKI team by being shown housing without full details behind lead treatment. Thus, criticism was made that both the children and parents were exploited by the study. Naturally comparisons were made to Tuskegee due to the similar affected demographics, lack of clear and explicit consent to participate in each study, lack of adequate care provided during each study, and the long-term, devastating impact of the study’s condition on the subject’s quality of life. Parallels between arguments of the implications and benefits of the research followed suit.

KKI saw extensive repercussions over the study. Class action lawsuit for deliberate exposure. Johns Hopkins Internal Review Board for allowing study to proceed in spite of federal regulations on using children as patients in studies. Argument of no risk in study since the adminstrators of study only reduced lead content and collected blood rather than explicitly inducing lead poisoning in children and that the parents ultimately still had the choice to live elsewhere.

The study had some defense, mainly regarding the takeaways that could be made based on the results. The results brought the benefit of understanding that lead paint quality/condition was more harmful than concentration of lead in paint due to increased likelihood of ingesting paint or dust from decaying paint. The growing criticism raised the concern that if zero risk was required in public health research then many problems could not be rigorously addressed, leaving the public collectively at risk. It was argued by the defense that the target population itself would still have a higher chance of exposure to lead poisoning regardless whether the study was implemented or not. Therefore, any of the techniques that proved effective and low cost would benefit more of the population in the long run. Thus, risk exposure guidelines could be revised as a sort of compromise. The idea of minimal risk to the patient was revisited and questioned to what extent a study’s procedure incurred risk, leading to changes in guidelines on how studies are conducted and more attention on current guidelines to avoid oversight of what minimal risk is acceptable.

https://www.ncbi.nlm.nih.gov/pubmed/15765579

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1508654/pdf/amjph00006-0020.pdf       

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3828970/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1447191/

http://www.sciencedirect.com/science/article/pii/S0892036202002362

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1733843/pdf/v030p00176.pdf