William Bragg

Sir William Henry Bragg (1862–1942) 600

Sir William Henry Bragg (1862–1942) was an English physicist, mathematician, and chemist

Bragg was a father to both crystal spectrometry and intermittent abdominal pressure ventilation.

His most famous work was within crystal spectrometry where his work with his son William Lawrence Bragg (1890-1971) went on to win them the Nobel Prize in Physics in 1915. Ironically, much of his early career was in the field of mathematics and Bragg was in fact completely ignorant of the field of physics! Bragg’s Law and the Bragg Spectrometer which bear his name, are testaments to his work in physics.

In the field of medicine, Bragg introduced one of the first intermittent abdominal pressure ventilators which was at odds with the current believes surrounding effectiveness of negative pressure ventilation. Bragg collaborated with English instrument maker Robert Paul to develop the Bragg-Paul Pulsator, the prototype of which utilised the bladder of two footballs with foot-operated bellows to facilitate ventilation.

The Pulsator was the forerunner of various other apparatus using the concept of abdominal pressure ventilation, the most famous was the Pneumobelt which continued to be manufactured up until 2008. The Pulsator helped save multiple lives during the Polio epidemic and whilst it is eclipsed in fame by the crystal spectrometer, it still holds an important part in medical history

  • Born on July 2, 1862 at Westward Cumberland, England.
  • 1881 – minor scholar of Trinity College, Cambridge studying mathematics under Edward John Routh (1837-1907)
  • 1885 – studied physics in the Cavendish Laboratory 
  • 1886 – University of Adelaide as Professor of Pure and Applied Mathematics with a subsidiary role in teaching physics. Interestingly, Bragg who was completely ignorant of physics, develops a flare for the subject and goes on to become one of the most eminent men in the field
  • 1887 – a founding member of the North Adelaide Lacrosse Club
  • 1895 – begins experimenting with Hertzian oscillators and radio transmission; meets Ernest Rutherford (1871-1937), a renown New Zealand Physicist (often called the ‘father of nuclear physics’) and begins a life-long friendship
  • 1896 – dabbles in X-ray spectrometry and obtains his first X-ray from his own Roentgen tube (assisted by AL Rogers). One of the early beneficiaries is his son who breaks his elbow and is photographed with this prototypal equipment. Bragg does not further his studies in X-rays until much later in his career
  • 1899 – his experimental work in radio transmission is successful and communications can now occur up to 8km (from the State Observatory to Henley Beach)
  • 1904 – gives a presidential address to the Australasian Association for the Advancement of Science (AAAS) at Dunedin New Zealand about his research in ionization of gases. This leads to a series of researches over three years which earns Bragg a fellowship of the Royal Society of London (FRS). He re-addresses the AAAS in Brisbane in 1909 summarizing his findings that X-rays and gamma rays are streams of neutral-pair particles rather than electromagnetic waves (a new and controversial perspective in the field of physics ). Returns to England
  • 1909-1915 Cavendish Professor of Physics at Leeds
  • 1912 – drawing inspiration from the work of Max Theodor Felix von Laue (1879-1960) work on X-ray diffraction by crystals, Bragg goes on to construct an X-ray spectrometer. Meanwhile his son William Lawrence adapts and simplifies the problems with Von Laue’s work and formulates…

Bragg’s Law

Bragg's Law schematic

Where λ is the wavelength of the x-ray; d is the spacing of the crystal layers (path difference); θ is the incident angle (the angle between incident ray and the scatter plane), and n is an integer.

This equation allows for details about crystal structure to be calculated or if structure is known, then for the wavelengths of the x-rays incident on the crystal to be determined. With this in hand, the father-son team go on to derive the atomic structure of crystals (such as ZnS) and begin the new subject of X-ray crystallography

  • 1913 – Bragg’s work in x-ray crystallography is temporarily halted by the outbreak of WW1. His attention instead turns to submarine detection by use of underwater sound
  • 1915 – Bragg and his son are awarded the Nobel Prize for Physics for their ‘services in the analysis of crystal structure by means of X-rays‘.
  • 1915-1925 Quain Professor of Physics at University College London; Fullerian Professor of Chemistry in the Royal Institution
  • 1920 – Knight Commander of the Most Excellent Order of the British Empire (KBE)
  • 1923 – Fullerian professor of chemistry and director of the Royal Institution of Great Britain; he helps to support multiple schools in X-ray crystallography. Bragg becomes the honorary doctor of some 16 universities
  • 1931Order of Merit
  • 1933 – invents the prototype for a novel respirator which utilises external positive pressure to facilitate respiration. He is inspired of the idea by his neighbour who suffered from muscular dystrophy and ventilatory failure. Bragg collaborates with instrument maker and ‘Father of the British Film IndustryRobert William Paul (1869-1943) to develop the “Bragg-Paul pulsator
  • 1937 – President of the Royal Society
  • Died on March 12, 1942

Medical Eponyms

Bragg-Paul Pulsator

I never saved a case before I got the Bragg-Paul Pulsator…and on behalf of 38 of my patients whose lives you have saved I thank you most profoundly.

Dr. C.J. McSweeny, and the diphtheria outbreak Cork Street Fever Hospital, 1938
The Bragg-Paul Pulsator 1934
The Bragg-Paul Pulsator 1934

The innovation of this ventilator was inspired by Sir Bragg’s neighbour Mr S. Crosby Halahan, who had muscular dystrophy and required intermittent periods of manually assisted mechanical ventilation. This progressed soon to continuous ventilation over a 18month period by two nurses and his (the neighbours’) wife who bore much of this intense labour

…for a long time two nurses were employed giving artificial respiration continually: the wife felt very much the disability of being unable to speak to him except in the presence of a nurse because of her strength had considerably diminished due to the strain of her husbands illness…

Letter from Bragg to Hill, 4th Jan 1934

Bragg thus devised an apparatus that could provide a better substitute to manual mechanical ventilation. He utilised the bladders of two footballs connected by tubing, bandaged one to the patient’s chest and the other was placed behind a pair of hinged boards which acted as rudimentary bellows. The operator could apply pressure to these bellows which caused the bladder attached to the patients’ chest to be rhythmically compressed. Thus, positive pressure ventilation is used to enforce expiration of air.

To better refine his apparatus, Bragg enlisted the help of scientist Robert William Paul whose addition of a hydraulic machine connected to the main water supply eradicated the need for external assistance to provide mechanical ventilation.

Paul retained the apparatus’s ability to be manually actuated in case of machine failure. He also improved upon the bladder attachment to the patient by using a rubber bag disguised as a hollow waist coat to be fastened around the chest with similar wide tubing connecting it to the bellows.

This new design worked effectively—except on occasions when the water pipes froze or the water supply was shut off for repairs without notice— and was estimated to have caused 15 million involuntary respirations in (the neighbours) lifetime

McGuire C. 2020

Later models were electrically powered and for good measure given the hydraulic powered version used about 700 gallons of water per day!

Bragg-Paul Pulsator 1939

The pulsator was a cheap and portable respirator in contrast to the Drinker respirator which were developed concurrently with the pulsator. The potential benefits of his invention lead Bragg to contact several hospitals to garner interest in the device.

It is most interesting to learn that so simple an apparatus has been used with such success. The principle of your arrangement seems to be just the opposite to that of the Drinker Respirator, but the same as artificial respiration as normally understood. I am sure that the details of your arrangement would be of immense interest and value to many Hospitals and Medical Men…

K.N Knapp of Swindon and North Wilts Victoria Hospital (letter to Bragg)

Before the pulsator could be readily distributed to hospitals, it had to undergo a series of physiological tests. The most notable collaborator of these was not ‘of the medical men’ but Mrs Phyllis Margaret Tookey Kerridge (1901-1940)

Phyllis M Tookey Kerridge (MA, Chemistry, PhD, MD) was a prominent scientist and member of the Royal College of Surgeons and Royal College of Physicians. Her modifications of the belt resulted in dramatic improvements in the ventilatory efficiency of the device, greater comfort for the patient to be able to withstand prolonged periods of pressure on the chest and allowed it to be adapted to newborns

The pulsator was never patented nor royalties received from its use. Its popularity was short lived and later superseded by the Both respirator in the 1940’s

Bragg X-ray spectrometer (1910)

Bragg developed his X-ray spectrometer at Leeds University, the prototype for all modern X-ray diffractometers. The spectrometer consists of a tube or collimator which contains two lead slits S1 and S2. An X-ray beam is passed through the tube and slits where it is made to fall on a crystal mounted on a turn table. The reflected beams pass through two other slits S3 and S4 into an ionization chamber.

Bragg x-ray spectrometer

The X-rays ionize the gas causing a current to flow between electrodes which is measured by a galvanometer. The turntable with the crystal is rotated to change the angles of the incident x-rays. Angles where strong reflections occur can be used to determine the interplanar spacing between atoms according to Bragg’s Law. By this means, the structure of a crystal can be derived.

Bragg X-ray spectrometer
Bragg’s X-ray Spectrometer

Major Publications


The Bragg-Paul pulsator met resistance among the medical community. Firstly, was the involvement of an engineer in its development (considered suspect); secondly, was the use of positive pressure ventilation which was argued to be ‘unnatural’ and thirdly, was the ‘unusualness’ of the invention.

The way that it made visible so clearly the process of forced breathing, without the apparent security and concealment offered by the more technologised devices, was uncomfortable to watch…I found myself unconsciously holding my breath while watching it and becoming increasingly conscious of my own breathing.

McGuire C. 2020
The patient is only partially enclosed. The first model is a Paul-Bragg pulsator; the chest is rhythmically subjected to positive pressure; the patient is not enclosed, instead he lies in an upright position. There are clear shots of the patient s chest rising and falling as well as the operation of the machine.

A committee was formed to investigate the debate of negative vs positive pressure ventilation in order to determine the standard of care for artificial respiration. Multiple respirators were tested including full body enclosure devices (Drinker, Emerson etc) and devices without full body enclosure (Bragg-Paul pulsator, Bustall Jacket etc).

The methodology and processes undertaken in this investigation were questionable and would probably not have met the ethical standards of today. Some examples include:

  • Recommendation for patients to wear ‘bedsocks’ to avoid chilled feet from the air that rushed in from the suction hole of the machine
  • Expectations that patients would ‘adapt’ their breathing to the machine and failure to synchronise would indicate ‘adequate power of natural breathing and does not require treatment in the machine.’ In order to try to facilitate this synchronisation, the breathing rate would be adjusted slowly without patient knowledge. In more extreme cases, the patients were sedated to force cooperation
  • The distress experienced by patients was waived in the report as ‘the relief afforded is so great and so sudden that any psychological stress is quickly banished’
  • That the noisiness of the machine would be conducive to deep sleeping

The report “Breathing Machines and their Use in Treatment” was published in 1939; no standard device was recommended although the conclusion reached was that use of any of these devices should occur in the hospital under medical expertise. Fortunately, technology and understanding about mechanical ventilation has progressed since then and patients are not required to ‘fit’ the technology rather the technology can be adapted to the patient.



Eponymous terms


the person behind the name

Emergency registrar at Sir Charles Gairdner Hospital, Perth

BA MA (Oxon) MBChB (Edin) FACEM FFSEM. Emergency physician, Sir Charles Gairdner Hospital.  Passion for rugby; medical history; medical education; and asynchronous learning #FOAMed evangelist. Co-founder and CTO of Life in the Fast lane | Eponyms | Books | Twitter |

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