The principle of transillumination by a glass rod, used more than twenty years ago by Rochon-Duvigneaud of Paris for the eye. and later improved by Würdemann, is not new; but the instruments utilizing this principle (including the Sachs lamp) are all expensive and need special lamps, batteries, wiring, etc. No doubt others have hit on the expedient which I have used now for about four years: the addition of the glass rod to the smallest of the common flash-lamps obtainable.
I take a small hard rubber syringe pipe, cut it off and drill out to fit tight over a piece of 3/16 inch glass stirring rod; cut the latter by nicking with a file to proper length, smooth the ends by melting in a gas or alcohol flame, and set firmly in place with collodion. The completed trans-illuminator is held in place over the end of the flash-lamp by a