Rather than write long pre-ambles, quoting Hippocrates or Galen or other surgeons and doctors on which much of 12th-century surgical knowledge was based, he gives clear and brief explanations for how to treat different illnesses and injuries. His writing provided the first Western European practical manual for teaching surgery. It was duplicated and used in universities at Bologna and Montpelier. Besides describing surgical techniques, he also described how medicines were prepared and applied, and how to diagnose illnesses. He was the first to use the word "lupus" to describe a rash that appeared on the cheeks.
In the 13th century, an Anglo-Norman translation was made and illustrated (above you see the dispensary and a doctor instructing his students). Though written in French, it was likely written in England because English terms are used throughout the text. This manuscript is now in the Trinity College Library collection. One of the delights of the illustrations is the facial expressions given to the patients, indicating the level of (dis)comfort they are going through. Also, surgical instruments are drawn with admirable accuracy.
(There are errors, however, due to sloppy reading of the text. One illustration is supposed to depict a condition that causes a blackened tongue, but the illustrator painted the tongue red. In another section on nasal polyps, the copyist did an "eye skip" where, while looking from original to copy, his eye skipped to a later occurrence of a word he just wrote, omitting the section in between. These errors can be determined by comparison to other manuscripts, and show that the copyist was not paying close attention to textual comprehension.)
Medieval surgeons were always looking for new ways to treat injury:
For example, it is believed that Roger of Salerno may have originated a technique for detecting a tear in the dura or cerebral membrane in skull fractures. Now known as the Valsalva maneuver, the doctor would have his patient hold their breath, introducing pressure into the skull, and the doctor would watch for air bubbles or cerebrospinal fluid leaking from the skull. Additionally, Roger was a pioneer in the treatment of nerve damage, advocating reanastomosis – the realignment of damaged tissue by surgical means – to repair severed nerves. [source]
The illustration of the dispensary above is in the section about treating fistula. This brings us to one of the most painful and "icky" treatments, but also to one of my favorite figures in medieval medicine, John Arderne, whom I'll tell you about tomorrow.