Martin W. Flack, CBE (1882

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A Moment in History

Jean George Bachmann
(1877 – 1959)

French physician–physiologist whose experimental work in the early twentieth century provided the first clear functional description of a preferential interatrial conduction pathway. This structure, eponymically named “Bachmann’s bundle”, plays a central role in normal atrial activation and in the pathophysiology of interatrial block and atrial arrhythmias.

As a young man, Bachmann served as a merchant sailor, crossing the Atlantic multiple times. He emigrated to the United States in 1902 and earned his medical degree at the top of his class from Jefferson Medical College in Philadelphia in 1907. He stayed at this Medical College as a demonstrator and physiologist. In 1910, he joined Emory University in Atlanta. Between 1917 -1918 he served as a medical officer in the US Army. He retired from Emory in 1947 and continued his private medical practice until his death in 1959.

On the personal side, Bachmann was a man of many talents: a polyglot, he was fluent in German, French, Spanish and English. He was a chef in his own right and occasionally worked as a chef in international hotels. In fact, he paid his tuition at Jefferson Medical College, working both as a chef and as a language tutor.

The intrinsic cardiac conduction system was a major focus of cardiovascular research in the late nineteenth and early twentieth centuries. The atrioventricular (AV) node was discovered and described by Sunao Tawara and Karl Albert Aschoff in 1906, and the sinoatrial node by Arthur Keith and Martin Flack in 1907.

While the connections that distribute the electrical impulse from the AV node to the ventricles were known through the works of Wilhelm His Jr, in 1893 and Jan Evangelista Purkinje in 1839, the mechanism by which electrical impulses spread between the atria remained uncertain.

In 1916 Bachmann published a paper titled “The Inter-Auricular Time Interval” in the American Journal of Physiology. Bachmann measured activation times between the right and left atria and demonstrated that interruption of a distinct anterior interatrial muscular band resulted in delayed left atrial activation. He concluded that this band constituted the principal route for rapid interatrial conduction.

Subsequent anatomical and electrophysiological studies confirmed the importance of the structure described by Bachmann, which came to bear his name. Bachmann’s bundle is now recognized as a key determinant of atrial activation patterns, and its dysfunction is associated with interatrial block, atrial fibrillation, and abnormal P-wave morphology. His work remains foundational in both basic cardiac anatomy and clinical electrophysiology.

Sources and references
1. Bachmann G. “The inter-auricular time interval”. Am J Physiol. 1916;41:309–320.
2. Hurst JW. “Profiles in Cardiology: Jean George Bachmann (1877–1959)”. Clin Cardiol. 1987;10:185–187.
3. Lemery R, Guiraudon G, Veinot JP. “Anatomic description of Bachmann’s bundle and its relation to the atrial septum”. Am J Cardiol. 2003;91:148–152.
4. "Remembering the canonical discoverers of the core components of the mammalian cardiac conduction system: Keith and Flack, Aschoff and Tawara, His, and Purkinje" Icilio Cavero and Henry Holzgrefe Advances in Physiology Education 2022 46:4, 549-579.
5. Knol WG, de Vos CB, Crijns HJGM, et al. “The Bachmann bundle and interatrial conduction” Heart Rhythm. 2019;16:127–133.
6. “Iatrogenic biatrial flutter. The role of the Bachmann’s bundle” Constán E.; García F., Linde, A.. Complejo Hospitalario de Jaén, Jaén. Spain
7. Keith A, Flack M. The form and nature of the muscular connections between the primary divisions of the vertebrate heart. J Anat Physiol 41: 172–189, 1907.

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Details: Written by: Efrain A. Miranda, Ph.D.; Published: January 15, 2026; Hits: 4107

This article is part of the series "A Moment in History" where we honor those who have contributed to the growth of medical knowledge in the areas of anatomy, medicine, surgery, and medical research.

Martin W. Flack, CBE
(1882 - 1931)

Martin William Flack, CBE (1882–1931), English physician and cardiovascular physiologist.

Born in 1882, in Borden, Kent, England. Flack studied Medicine and Surgery at Oxford University, graduating in 1908. While still a medical student at the London Hospital, Flack began his most important research under Arthur Keith’s guidance. In 1906 while examining histological glass slides of the heart of a mole, Flack identified a distinct cluster of specialized cardiac muscle cells at the junction of the superior vena cava and the right atrium. Working with Keith they realized that this was the source of the heartbeat. They termed this structure the “sino-auricular node”, known today as the sinoatrial node, and published their description in 1907, completing the anatomical mapping of the heart’s conduction system following earlier work on the atrioventricular node by Sunao Tawara.

Following this discovery, Flack continued in academia as demonstrator of physiology (1905–1911) and later as lecturer (1911–1914) at the London Hospital. He coauthored “A Textbook of Physiology” in 1919 and conducted research on the physiological responses of the sinoatrial node to temperature, mechanical stimulation, and pharmacological agents in the early 1910s, demonstrating its functional characteristics.

During World War I, Flack served on the Medical Research Council and contributed to studies concerning cardiorespiratory physiology. In 1919, he was appointed Director of Medical Research for the Royal Air Force where he conducted research on the physiological performance of pilots at high altitudes and on methods to assess pilot fitness, including cardiac and respiratory functions. His contributions to medical research and service were recognized with appointment as a Commander of the Order of the British Empire (CBE)

Sources:
1. Mohr PD. Illustrations of the heart by Arthur Keith: His work with James Mackenzie on the pathophysiology of the heart 1903–1908. J Med Biogr. 2021;30(3):193–201
2. Silverman ME, Hollman A. Discovery of the sinus node by Keith and Flack: on the centennial of their 1907 publication. Heart. 2007;93(10):1184–1187.
3. Keith A, Flack M. The Form and Nature of the Muscular Connections between the Primary Divisions of the Vertebrate Heart. J Anat Physiol. 1907 Apr;41(Pt 3):172-89. PMID: 17232727; PMCID: PMC1289112.
4. Keith A, Flack M. The form and nature of the muscular connections between the primary divisions of the vertebrate heart. J Anat Physiol 1907;41: 172–189
5. Dawadi, P; Khadka, S. Research and Medical Students: Some Notable Contributions Made in History. JNMA J Nepal Med Assoc. 2021 Jan 31;59(233):94–97

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Martin W. Flack, CBE (1882–1931)

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