Thursday, March 08, 2012

1854: M. Priory fine tunes stethoscope and percussion

Pierre Adolph Priory (1794-1879)
Joseph Auenbrugger, Jean Corvisart, and Rene Laennec introduced the medical community to the technique of chest percussion, and the invention of the stethoscope to improve the technique of auscultation.  Both techniques became valuable for helping physicians diagnose diseases of the chest, although both needed to be perfected.  

By the time of his death in 1826, Rene Laennec saw his invention of the stethoscope become accepted by his peers.  However, he would readily admit that his new tool was not yet perfected. He would spend many hours himself improving upon it, and when he died this task was left to his peers.

Pierre Adolph Piorry (or M. Priory, with the M. coming from his French name) was born in 1794, served in the Napoleanic wars in Spain, and served at the Atarazanas Hospital in Spain where he was able to witness military surgery." In 1814 he returned to his medical practice in France, and, like Laennec, served as a student of Corvisart. He qualified as a physician in 1816, the same year Laennec invented his stethoscope.  (1, page 675)

This is a picture of the Priory binaural stethoscope complete with
the pleximeter(round, solid ivory disks on bottom second from left)
and fingerthimble ivory percussor (on botton right).  Picture from 1828.
Photo from
He had a gift as a teacher, and between 1817 and 1826 he delivered lectures on physiology and pathology.  In 1826 he was appointed physician to the Paris Hospital.  In 1837, after many years of attempting to do so, he became professor of medicine at Paris School of Medicine (l'Hospital de la Pitie, Paris).  He was 43.  (1, page 676)

He then took off where Laennec left off, working hard to fine tune the binaural stethoscope.  The product he ended up with would be the general design of most stethoscopes used for the rest of the 19th century.  He also worked to improve the technique of percussion.  His work in this area created excitement for the remainder of the century, it would ultimately be for naught. (1, page 675)

A Classic Reprint Series of Priory's book
is proof his ideas are still sought after.
The first edition was published in 1826.
His stethoscope was trumpet shaped and made of wood, although it was shorter and thinner than Laennec's.  It came with a removable wood plug, ivory earpiece and chest piece, with the chest piece also serving as a pleximeter (described below).  This design was also much more pleasing to physicians, and was much easier to carry in their bags. (5)

In a 1979 Biography of Priory, Alex Sakula said of Priory
Priory, enthused by Laennec's invention, developed an ambition to emulate the great master and to achieve fame in some similar fashion. Priory describes in his poem Dieu L'ame et Nature how he came to study percussion.  He prayed to God asking to be able to make some discovery like that of Laennec.  A few months later, he had slight pruritus and while scratching the skin over his chest he heard a sound.  He interposed a coin and scraped it and obtained a stronger sound, which varied according to the density and elasticity of the underlying organ." (1, page 577)
This is a picture of Priory's Pleximeter. (5, page 311)
Sakula said that the next day he began his work on percussion, and hoped that what Laennec had done for auscultation he could do for percussion.  On February 28, 1826, he read "read a prize winning paper on his new method of percussion to the Academie Royale de Medecine.  Laennec (then very near his death) was one of those present." (1, page 577)

Scott Alison, in his 1861 book, "The physical examination of the
 chest," described the procedure of percussion as follows: 
 The pleximeter is to be placed in or over an intercostal space,
 or upon a flat surface, and fitted well with gentle pressure upon
 the body,and held by the thumb and forefinger of the left hand. 
It may be employed together with a hammer or with the fingers." 
A percussion hammer is sown here.  (5, page 311
In the paper, Sakula said, he described his new technique of doing percussion, which involved placing a small plate between the patient's skin and the percussing finger.  He called the plate a pleximeter from the Greek w``ords to strike and to measure. (1, page 577)

As Laennec experimented with various materials while trying to perfect his stethoscope, Priory experimented with various materials while trying to perfect his pleximeter, said Priory, "but finally settled on a small ivory plate, 5 cm in diameter.  He also devised a combined stethoscope and pleximeter made of ivory and cedar wood." (1, page 577)

This little gadget shows the extent that some physicians went to 
create the perfect pleximeter.  Scott Alison described it as:
"An instrument combining both a pleximeter and a hammer 
was contrived by Dr. Aldis some years ago. It consistsof a
 hammer moving on a fulcrum, and of a disc of cork which 
receives the blow of the hammer. The cork disc is placed 
upon the chest, and the hammer is raised by the finger to the
 required height. The higher the hammer is raised, the more force
 is obtained. The hammer falls by the operation of a spring.
 Great uniformity of blow is obtained by this instrument. 
This ingenious contrivance has obtained the name of 
echometer." (5, page 312)

After all the publicity that that stethoscope had garnished since Laennec introduced it in 1819, percussion had lost some of its luster.  Some probably believed the stethoscope would replace it completely.  (1, pages 576-577)

However, Sakula said:
"Piorry did not regard percussion as competing with auscultation, and taught that the two techniques were supplementary one to another." (1, page 577)
These are a few of the varieties of wooden binaural stethoscopes
in use by physicians as of 1861. (5, page 316)
There were still many physicians who did not adapt his stethoscope and pleximeter.  Many who finally accepted his research on percussion came up with their own techniques for performing the procedure.  For instance, the preferred method became the use of the finger of one hand used as the pleximeter, and the finger of the other hand as the percussor.  Yet the principle is the same.  (1, page 577)

This is a flexible stethoscope.  In his 1861 book, Scott Alison said,
"In employing the flexible stethoscope, it is even more necessary
than in the case of the wooden instrument to observe that the object
end is well applied so as to close the tube.  If left partially open,
scarcely any sound is perceived. (5, page 321)
The Cyclopaedia of Practical medicine, edited in part by John Forbes, best concludes the accomplishments of Priory regarding percussion: (3, page 7)
M. Priory, a young Parisian physician, has the honor of having, if not invented, at least brought into a formal and matured shape, this new application of the discovery of Auenbrugger, and with practical results greater precision and importance than could have been anticipated. (3, page 7)
Dr. Sibson's pleximeter 
consists of a plate of 
ivory which receives
the blow, and of a brass
hammer or weight
working in a metal frame.
. The weight or hammer
is raised by the fingers;
these being removed, 
the weight or hammer 
falls upon the ivory plate
by the elasticity of an
indiarubber band connecting 
the weight or hammer 
with the ivory plate.
The hammer works
to the plate. (5, page 313
Like many new tools invented or discovered to assist physicians do their jobs better, the Priory stethoscope and pleximeter were not accepted by all physicians.

Piorry remained a famous physician until his retirement at the age of 72 in 1866.  He died at age 85 in 1879.

Most stethoscopes used for the remainder of the 19th century after Piorry's death were based on his design, designed by various physicians, produced by various manufacturers, made of various materials, and scattered throughout various publications. Some of these other binaural stethoscopes were made by Quain, Stokes, Arnold, Barclay, Elliotson, Dobell, Loomis, Burrow, Clark, Camman, and Furguson. (4, page 626)

Yet long before he passed from this world his hard work paid off.  By 1854 percussion had been fine tuned so that it was often performed not just over the chest, but over various organs of the body to help doctors diagnose any pathological disorders.

And his stethoscope remained the most popular one used for the remainder of the 19th century.  There were many similar versions by various manufacturers, although most of them are simply adaptations of the binaural stethoscope that M. Priory fine tuned.

  1. Sakula, Alex., "Pierre Adolphe Piorry (1794-1879): pioneer of percussion and pleximetry," October, 1979, Thorax ( 34(5): 575–581).  
  2. "The Binaural Stethoscope,",, information reviewed March 8, 2012
  3. Forbes, John, Alexander Weedie, Conolly, editors, "The cyclopaedia of practical medicine," volume 1, London, 1833
  4. Camman, Donald M, "Historical Sketch: Stethoscopes," A Reference Handbook for Medical Sciences, edited by Albert Henry Buck, by various writers, volume VI, 1888, New York, William Wood and Company, 626-628
  5. Alison, Somerville Scott, "The physical examination of the chest in pulmonary consumption and its intercurrent diseases," 1861, London, John Churchill

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