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e EXPERIMENTS WITH SALINE SOLUTIONS 235 
ture, or exposed to diffuse daylight at the ordinary 
temperature of the air. 
The Influence of Diffuse Daylight. 
Comparative trials were made in order to ascer- 
tain whether the heat of an incubator at 90-100 F. 
(32°-37  C.), associated with darkness, or a much 
lower temperature, plus the influence of diffuse day- 
light, would prove most influential in leading to 
the appearance of organisms in the experimental 
fluids. I soon found that no general rule in regard 
to this could be laid down—that heat and darkness 
was more favourable with a few of the solutions, and 
that diffuse daylight, even with a very much lower 
temperature, was more productive with most of the 
others. 
This favourable influence of diffuse daylight in 
promoting the growth, and possibly the origination, of 
micro-organisms is a new point, never, | believe, pre- 
viously noted by bacteriologists. It seems, indeed, 
to be contrary to their generally accepted views, 
since we find Dr Allan Macfadyen saying in a 
lecture at the Royal Institution, delivered in June 
1900, that, ‘ Direct sunlight was a most deadly 
bactericidal agent, and diffuse light was also injuri- 
ous, though slower in action.” 
Its favourable influence was first discovered 
by me early in 1905, when studying the growth 
and multiplication of common Bacteria in a simple 
solution of ammonium tartrate in distilled water. 
1 The Times, June 11, 1900, and Proceedings, vol. xvi., p. 451. 
