Magic Carpet III: Clearing Stagnant Air and Measuring Blood Pressure in the 1730s: The Reverend Steven Hales

??????????? In this edition of the Magic Carpet, Magic Carpet III, we travel back to the mid-1700s, 1738 A.D. to be exact, to the town of Teddington, which is an ancient Parish in Middlesex County, England (Saxon 969A.D.) located some 12 miles south and west of London. Here we’ll meet up with the Reverend Steven Hales D.D., who is recognized for his amazing contributions to physiology, health, botony, and faith. It is the intent of the MAGIC CARPET series to take us back in time and to briefly review incredible, innovative, transformative research that truly changed the course of medicine and surgery. As previously described, the main inclusion criterion for this post involves the transformation of novel ideation into clinical product that has meaningfully impacted clinical care. This story is no exception, and for this reason, Reverend Steven Hales should be on your list of professional heroes. Here we go…

??????????? Teddington, England, 1738. According to the Parish register, there are 119 families, 471 inhabitants, 175 being under 16 years of age. The number of males in the parish was 212 and females 259. There were 82 married couples, nine widowers, and 35 widows. [1] It was in this environment that The Reverend Hales served as the parish priest or “perpetual curate.” [2] Hales was an exceedingly well-educated individual having studied mathematics, natural sciences, and philosophy at Cambridge in the late 1690s, and in 1709, became an ordained Priest. [3] While clearly well-studied, Hales lacked focus, and because of this, he successfully contributed to a host of different interest areas including: Our understanding of the movement of water within plants and the importance of sunlight to plant growth, mitigating the burden of disease caused by “bad air”, the distillation of fresh water from salt water, and importantly, he was the first to measure blood pressure, pulsatility, cardiac output, the function of cardiac valves, and critical early observations around the physiologic effects of exsanguination (hemorrhage and hemorrhagic shock): [3]

“11. When between fourteen and fifteen Quarts of Blood had been evacuated, and thereby the Force of that which remained in the Vessels greatly decreased, then the Mare fell into cold clammy Sweats, such as frequently attend dying Persons.- Hales 1833" [3,7]

??????????? In keeping with our series’ goal of brief, impactful, descriptions of critical clinical innovations, in this edition of the Magic Carpet, we’ll focus on two of Hales’ most important contributions to medicine:?

1.???? Mitigating disease caused by “bad air”

2.???? The measurement of blood pressure and pulsatility

??????????? While controversial, I believe that Hales’ work in the area of ventilation edges out his work in the area of blood pressure measurement relative to its overall impact on public health. Although Hales was not alone in his view that “bad air” played a role in disease and disease spread, his approach to mitigating its impact by creating ventilation systems for confined spaces, such as within hospitals, is laudable, and without question reduced disease burden when used. [4,5,6] What follows is the title page of his amazing work and his focus on ventilating hospital rooms specifically. (The full content is available in ref. 6 below)

Now as to the measurement of blood pressure (and cardiac cannulation), the Reverend Hales would be the first to do so, and is thus recognized for his incredible contributions to physiology and medicine, and he did so in 1733, in a paper entitled:

This amazing work, which was performed in live mares and other animals, also includes what is (may be) the first invasive measurement and description of the pulsatile nature of mammalian circulation.

?“1. In December, I caused a mare to be tied down alive on her back, she was 14 hands high, and about 14 years of age, had a fistula on her Withers, was neither very lean, nor yet lusty: having laid open the left crural artery about 3 inches from her belly, I inserted into it a brass pipe, whose bore was 1/6 of an inch in diameter; and to that, by means of another brass pipe, which was fitly adapted to it, I fixed a glass tube, of nearly the same diameter, which was 9 feet in length; then untied the ligature on the artery, the blood rose in the tube 8’3” perpendicular above the level of the left ventricle of the heart: but it did not attain to its full height at once; it rushed up about halfway in an instant, and afterwards gradually at each pulse 12, eight, six, four, two, and sometimes 1 inch: when it was at its full height, it would rise and fall at an after each pulse two, three, or 4 inches; and sometimes it would fall 12 or 14 inches, and have there for a time the same vibrations up and down at, and after each pulse, as it had, when it was at its full height; which it would rise again, after 40 or 50 pulses.

2. The pulse of the horse that is well, and not terrified, nor in pain, is about 36 beats in a minute, which is nearly half as fast as the pulse of a man in health: this mare’s pulse beat about 55 times in a minute, and sometimes 60 or 100 she being in pain.”

There are several other experiments within this text, which can be read in full (see ref. 7), that describe Hales’ measurement of cardiac output using wax casts of the ventricles, in addition to his observations associated with exsanguination and more!

For now, I leave you with the following. The next time you enter the hospital and note clean “fresh” air OR you measure a pulse or blood pressure by any means, honor the Reverend Doctor Stephen Hales by remembering his amazing work and contributions. I know I do.

Post Script

I imagine that animal experimentation in the 1730s was discouraged and might have been viewed as pagan or worse by others. Of course, being a revered and respected Reverend, Hales might simply have “gotten away with it.” Clearly, his work displeased some, as evidenced by the writings of Alexander Pope, who apparently was both a friend of Hales and loved dogs: "He commits most of these barbarities with the thought of its being of use to man. But how do we know that we have a right to kill creatures that we are so little above as dogs, for our curiosity, or even for some use to us?" [3]

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References and Sources:

1.???? https://www.british-history.ac.uk/london-environs/vol3/pp503-516#anchorn33

2.???? Wikipedia contributors. (2023, November 2). Stephen Hales. In?Wikipedia, The Free Encyclopedia. Retrieved 21:20, March 17, 2024, from?https://en.wikipedia.org/w/index.php?title=Stephen_Hales&oldid=1183077803

3.???? Wikipedia contributors. (2023, November 2). Stephen Hales. In?Wikipedia, The Free Encyclopedia. Retrieved 21:20, March 17, 2024, from?https://en.wikipedia.org/w/index.php?title=Stephen_Hales&oldid=1183077803

4.???? University of Minnesota: Reverend Stephen Hales on Blood Pressure https://www.epi.umn.edu/cvdepi/essay/reverend-stephen-hales-on-blood-pressure/

5.???? Royal Collection Trust Stephen Hales https://www.rct.uk/collection/1090221/a-description-of-ventilators-whereby-great-quantities-of-fresh-air-may-with-ease

6.???? A description of ventilators: whereby great quantities of fresh air may with ease be conveyed into mines, goals [sic] hospitals, work-houses and ships, in exchange for their noxious air. An account also of their great usefulness in many other respects. As in preserving all sorts of grain dry, sweet, and free from being destroyed by weevils, both in grainaries and ships, and in preserving many other sorts of goods. As also in drying corn, malt, hop, gun-powder, &c., and for many other useful purposes / Which was read before the Royal Society in May, 1741 ... By Stephen Hales.?Public Domain Mark. Source: Wellcome Collection. Available from: https://wellcomecollection.org/works/fh58ynas/items

7.???? Biodiversity Heritage Library. Statical essays, containing haemastaticks, or, An account of some hydraulick and hydrostatical experiments made on the blood and blood vessels of animals : also an account of some experiments on stones in the kidneys and bladder : with an enquiry into the nature of those anomalous concretions : to which is added, an appendix, containing observations and experiments relating to several subjects in the first volume, the greater part of which were read at several meetings before the Royal Society : with an index to both volumes

Vol. II https://www.biodiversitylibrary.org/item/188045#page/5/mode/1up

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