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".

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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Menynx / Meninges

First used by Galen, the term [menynx] is Greek and means "membrane", referring initially to any body membrane. Erasistratus (c. 300 B.C.) used the term [menynx] to refer to a membrane covering of the brain and spinal cord and has been used so since then.

The plural form of [menynx] is [meninges]. The plural form is common, but the singular form [menynx] is usually used incorrectly as [meninge].

There are three meninges that cover the spinal cord and brain. From deep to superficial:

•Pia Mater: Latin terms meaning "tender mother" it is a thin membrane covering the outer layer of the spinal cord and brain intimately and not easily dissectable from the organ.

Arachnoid mater: The term refers to the spider-web look of this vascular menynx.

Dura mater: Latin terms meaning "tough mother". The dura mater is the outermost layer and is quite tough, forming a sac containing the spinal cord and brain, the dural sac or thecal sac. The images depict two famous sketches by Andrea Vesalius. The superior image shows a head with the dura mater in situ (label "A"). The second image show the dura mater open (label "H") and the vessels associated with the arachnoid layer.

Between the arachnoid mater and pia mater there is a "space" filled with fluid. The space is called the subarachnoid space and the fluid is the cerebrospinal fluid

Original images from Andreas Vesalius' "De Humani Corporis Fabrica; Libri Septem" (1543) 

Brain dissection. dura mater in situ (Vesalius)Brain dissection. dura mater open (Vesalius)
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