The writer explains the origin of the scale measuring the external diameter of different types of bougies, catheter or probes. That scale has turned out to be an essential tool for the best of several specialities created in the 19th century, namely urology. An instrument maker close to the surgeons whose ideas he would quickly grasp, Joseph F. B. Charriere, proposed a scale with thirty holes that would make it possible to get external gauge of the third of a millimetre. Several people tried to imitate his device but his scale was eventually recognized as the most efficient one all over Europe, accepted even by the British and then the Americans. Its usefullness goes on to this day as the French scale has become universal together with the unit that it entails, the Charrire unit, which is still the reference to measure all the diameters used by surgeons and doctors.
作者解释了测量不同类型探条、导管或探头外径的刻度的起源。事实证明，该刻度是19世纪创建的几个最佳专业领域（即泌尿外科）的重要工具。仪器制造商约瑟夫·F·B·沙里耶（Joseph F. B. Charriere）与外科医生关系密切，能迅速理解他们的想法，他提出了一种有30个孔的刻度，这使得获得三分之一毫米的外径测量成为可能。有几个人试图模仿他的装置，但他的刻度最终在全欧洲被公认为最有效的，甚至被英国人和美国人所接受。它的实用性一直延续到今天，因为法国刻度连同其所包含的单位——沙里耶单位一起变得通用，沙里耶单位至今仍是测量外科医生和医生所使用的所有直径的参考标准。
