Medical Terminology Daily (MTD) is a blog sponsored by Clinical Anatomy Associates, Inc. as a service to the medical community. We post anatomical, medical or surgical terms, their meaning and usage, as well as biographical notes on anatomists, surgeons, and researchers through the ages. Be warned that some of the images used depict human anatomical specimens.

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A Moment in History

Jean-Louis Petit

Jean Louis Petit
(1674 – 1750)

French surgeon and anatomist, Jean Louis Petit was born in Paris in on March 13, 1674.  His family rented an apartment at his house to Alexis Littre (1658 – 1726), a French anatomist. Petit became an apprentice of Littre at seven years of age, helping him in the dissections for his lectures and at an early age became the assistant in charge of the anatomic amphitheater.

Because of Petit’s dedication to anatomy and medicine, in 1690 at the age of sixteen, became a disciple of a famous Paris surgeon, Castel.

In 1692, Petit entered the French army and performed surgery in two military campaigns. By 1693 he started delivering lectures and was accepted as a great surgeon, being invited to the most difficult operations.  In 1700 he was appointed Chief Surgeon of the Military School in Paris and in the same year he received the degree of Master of Surgery from the Faculty of Paris.

In 1715 he was made a member of the Royal Academy of Sciences and an honorary member of the Royal Society of London. He was appointed by the King as the first Director General of the Royal Academy of Surgery when it was founded in 1731.

Petit’s written works are of historical importance.  “Traite des Maladies des Os” ( A Treatise on Bone Diseases);  “Traite des Maladies Chirurgicales et des Operation” (A Treatise on Surgical Diseases and their Operations” This last book was published posthumously in 1774. He also published a monograph on hemorrhage, another on lachrymal fistula, and others.

He was one of the first to perform choIecystotomy and mastoidotomy. His original tourniquet design for amputations saved many in the battlefield and the design of the same surgical instrument today has not changed much since its invention by him.

His name is remembered in the lumbar triangle, also called the "triangle of Petit", and the abdominal hernia that can ensue through that area of weakness, the lumbar hernia or "Petit's hernia".

Sources:
1. “Jean Louis Petit – A Sketch of his Life, Character, and Writings” Hayne, AP San Fran Western Lancet 1875 4: 446-454
2. “Oeuvres compl?tes de Jean-Louis Petit” 1837 Imprimerie de F. Chapoulaud
3. Extraits de l'eloge de Jean-Louis Petit Ius dans Ia seance publique de I' Academie royale de chirurgie du 26 mai 1750” Louis A. Chirurgie 2001: 126 : 475- 81


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Brachialis

Brachialis muscle - Image modified from the original. Public domain
Brachialis muscle.
Click on the image for a larger depiction

UPDATED: The brachialis muscle is a skeletal muscle attached proximally to the anterior surface of the humerus and distally to the coronoid process and tuberosity of the ulna. It is one of the three muscles in the anterior compartment of the arm (flexor compartment), the other two being the biceps brachii and the coracobrachialis.

It is a strong flexor of the elbow found deep to the biceps brachii. Because it does not attach to the radius, the brachialis muscle does not participate in the pronation and supination of the forearm.

The brachialis is supplied by branches of the brachial artery and by the recurrent radial artery.

The innervation of the brachialis muscle is a point to be discussed. Most modern books of anatomy state that this muscle is innervated by the musculocutaneous nerve (C5, C6, and C7). Older and more detailed books state that this muscle has a dual innervation. A 2011 research paper published in Spanish (see Sources #6) describes this dual innervation. The proximal portion of the muscles is indeed innervated by the musculocutaneous nerve, but the distal portion (in 90% of the cases) is innervated by muscular branches that arise off the radial nerve. The radial nerve (C5, C6, C7, C8 & T1) is a branch of the brachial plexus.

Following is an excerpt from the "Trail Guide to the Body" by Andrew Biel: "Ironically, (because it is deep to the biceps) the brachialis girth only helps the biceps brachii to bulge further from the arm, making the brachialis the biceps' "best friend"

Personal note: The research paper that describes the double innervation of the brachialis muscle was done at my alma mater, the University of Chile, and the authors' listing includes two of the contributors to this blog, Professors Claudio Molina and Cristian Uribe. Dr. Miranda

Sources:
1. “Gray’s Anatomy” Henry Gray, 1918
2. "Tratado de Anatomia Humana" Testut et Latarjet 8th Ed. 1931 Salvat Editores, Spain
3. "Gray's Anatomy" 42nd British Ed. Churchill Livingstone 2021
4. “An Illustrated Atlas of the Skeletal Muscles” Bowden, B. 4th Ed. Morton Publishing. 2015
5. "Trail Guide to The Body" 4th. Ed. Biel, A. Books of Discovery. 2010
6. "Doble Innervacion del Musculo Brachial en la Poblacion Chilena" Claudio Molina; Cristián Uribe; Álvaro Heras; Cristián Astorga;Jorge Lemus & Alberto Rodríguez. Int. J. Morphol, 2011. 29(4):1207-1211. A PDF copy of this paper is available here.

Note: The side image modified from the original by Anatomography, CC BY-SA 2.1 JP <https://creativecommons.org/licenses/by-sa/2.1/jp/deed.en>, via Wikimedia Commons following Creative Commons attributes.