ATMOSPHERE IN RELATION TO PUTREFACTION AND INFECTION. 
73 
but obliterated, while in the sixth flask, seven days old, it was entirely shattered, the 
turbid medium being filled uniformly with the laterally scattered light. 
Two of these flasks were of a bright yellow-green colour, two were milky or white, 
and two of a dull brownish hue. 
Cohn mentions the bluish tinge of the infusion by reflected and its yellow tinge by 
transmitted light when the Bacteria are incipient. This is due to a dichroitic action, 
similar to that which produces the blue of the sky and the morning and evening red. 
The blue, however, though discernible, is not pronounced, for the Bacteria are too large 
to scatter the colour in any high degree of purity ; but with a “ muddy ” infusion a very 
fair red may be obtained from transmitted light. I have used the Bacterial turbidity 
for photometric purposes. On the 9th of October, for example, I accompanied Sir 
Bichard Collinson and a Committee of the Elder Brethren of the Trinity House to 
Charlton, with the view of comparing together two lights mounted at the Trinity Wharf 
at Blackwall. To imitate a foggy atmosphere, I employed an infusion cloudy with 
Bacteria and placed in a glass cell. With it the beams could be toned gradually down 
to complete extinction. 
Note II. Fluorescence of Infusions. 
All the animal infusions, both flesh and fish, showed the same fluorescence. It was 
the same green hue throughout, though of varying degrees of intensity. In wild duck, 
grouse, snipe, hare, partridge, and pheasant the fluorescence was fine — sometimes exceed- 
ingly fine. In rabbit it was less fine than in hare, and in a tame rabbit less fine than in 
a warren rabbit. Fishes also differed from each other. Mullet, for example, was finer 
than cod, herring, or haddock. Beef, mutton, heart, liver all showed the same green 
fluorescence. 
Led up to it by a series of remarkable experiments on the rapidity of the passage of 
crystallized substances into the vascular and non-vascular textures of the body*, 
Dr. Bence Jones and Dr. Dupre communicated to the Boyal Society in 1867 a highly 
interesting paper “ On a Fluorescent Substance, resembling Quinine, in Animals ’’f. 
They then showed that “from every texture of man and of some animals a fluorescent 
substance can be extracted, which, when extracted, has a very close optical and chemical 
resemblance to quinine.” They therefore called it animal quinoidine. In dilute solu- 
tions they found that the fluorescence of the animal substance was not to be distinguished 
from that produced by quinine. When the solution was concentrated, the colour of the 
light was of a decidedly greenish hue. This latter observation is most in agreement with 
mine. In all the infusions examined by me the fluorescent light was a decided green, 
and not to be mistaken for the blue light of quinine. 
The green colour is similar to that emitted by the crystalline lens when a beam of 
* Proceedings of the Royal Society, vol. xiv. 1865. 
t Ibid. vol. xv. p. 73. 
