ult to the intelligence of the
physician to say that he cannot master a simple problem of electric
testing involving the locating of one or more of five possibilities.
It is simply a matter of memorizing five tests. It is repeated for
emphasis that a commercial current reduced by means of a rheostat
should never be used as a source of current for endoscopy with any
kind of instrument, because of the danger to the patient of a possible
"grounding" of the circuit during the extensive moist contact of a
metallic endoscopic tube in the mediastinum. The battery shown in Fig.
8 should be used. The most frequent cause of trouble is the mistake of
over-illuminating the lamps. _The lamp should not be over-illuminated
to the dazzling whiteness usually used in flash lights_. Excessive
illumination alters the proper perception of the coloring of the
mucosa, besides shortening the life of the lamps. The proper degree of
brightness is obtained when, as the current is increased, the first
change from yellow to white light is obtained. Never turn up the
rheostat without watching the lamp.

_Testing for Electric Defects_.--These tests should be made
beforehand; not when about to commence introduction.

If the first lamp lights up properly, use it with its light-carrier to
test out the other cords.

If the lamp lights up, but flickers, locate the trouble before
attempting to do an endoscopy. If shaking the carrier cord-terminal
produces flickering there may be a film of corrosion on the central
contact of the light carrier that goes into the carrier cord-terminal.

If the lamp fails to show a light, the trouble may be in one of five
places which should be tested for in the following order and manner.
1. The lamp may not be firmly screwed into the light-carrier.
Withdraw the light-carrier and try screwing it in, though not too
strongly, lest the central wire terminal in the lamp be bent over.
2. The light-carrier may be defective.
3. The cord may be defective or its terminals not tight in the
binding posts. If screwing down the thumb nuts does not produce a
light, test the light-carrier with lamp on the other cords. Reserve
cords in each pair of binding posts are for use instead of the
defective cords. The two sets of cords from one pair of binding posts
should not be used simultaneously.
4. The lamp may be defective. Try another lamp.
5. The battery may be defective. Take a cord and light-carrier with
lamp that lights up,