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two carbon electrodes. This is borne out clinically when the two
sources of illumination are compared by the more rapid and more
pronounced erythema resulting from exposure to the carbon-iron
combination.
The bactericidal power of the rays emitted was roughly
measured by exposing a culture of Staphylococcus Aureus. An
emulsion of this organism was dried on to one side of a sterile
coverslip, and a series of such coverslips exposed at six inches
distance from the arc. The coverslips were then incubated in
broth.
24 hours 48 hours
Exposed for 2½ minutes at 6 ins slight growth good growth
5 „ „ no „ growth
„ 15 „ „ „ „ „
„ 20 „ „ „ „ „
„ 25 „ „ „ no growth
Pacini states that Staphylococcus Aureus exposed to the
rays of a mercury vapour lamp at five inches distance from the
lamp is killed in 1½ minutes.
A rough comparison between these lamps and Bermondsey
sunlight is given by the following experiment: —A quartz tube
containing Acetone Methylene Blue solution was exposed to the
lamp at six inches distance for 30 minutes, and gave a reading
of 2. The same tube exposed for one hour to bright sunlight on
31st August between 3.30 and 4.30 p.m. (summer time) gave a
similar reading of 2.
During the course of the year 69 patients have been treated.
There is a morning and afternoon session each day, with the
exception of Thursday afternoon, which is replaced by an evening
session on Wednesday. There is a session on Saturday morning.
Every patient attends at least three times a week, and a considerable number attend daily. In all cases a general light bath is
given, the patient sitting before the lamp naked except for bathing
slips, socks, and goggles. These lamps are not adapted for local
treatment. Each patient is treated individually, but as a routine
we begin with five minutes' exposure at two feet (2½ minutes
front and 2½ minutes back), and proceed by daily increments of