From The Case of Oscar Brodski (c.1912) by R. Austin Freeman:
"May I trouble you for your lens, Jervis?" he said; and, as I handed him my doublet ready opened, the inspector brought the lantern close to the dead face and leaned forward eagerly. In his usual systematic fashion, Thorndyke slowly passed the lens along the whole range of sharp, uneven teeth, and then, bringing it back to the centre, examined with more minuteness the upper incisors. At length, very delicately, he picked out with his forceps some minute object from between two of the upper front teeth and held it in the focus of the lens. Anticipating his next move, I took a labelled microscope-slide from the case and handed it to him together with a dissecting needle, and, as he transferred the object to the slide and spread it out with the needle, I set up the little microscope on the shelf.
"A drop of Farrant and a cover-glass, please, Jervis," said Thorndyke.
I handed him the bottle, and, when he had let a drop of the mounting fluid fall gently on the object and put on the cover-slip, he placed the slide on the stage of the microscope and examined it attentively.