98 TRANSACTIONS OF THE [MAR. 11 
Action on Milk.—According to the descriptions, in milk “ the 
casein is slowly precipitated, and later is peptonized witha neu- 
tral or alkaline reaction.” This is the usual course; but there is 
never a distinct coagulum, even on boiling. The ‘milk usually 
assumes a watery appearance, with a slight amount of white 
sediment, which is gradually dissolved. Cultures 3,5 and 7 pro- 
duced no perceptible change in milk; again in3,a slight sediment 
was observed, but no coagulum on boiling. Culture 6 rendered 
the milk very watery. In appearance the contents of the tube 
were two-thirds of a water v fluid, colored pink and one-third of 
a flaky coagulum; but on shaking up and boiling, the coagulum 
was seen to have no consistence. 
Reduction of Nitrate.—Nitrates are usually quickly and thor- 
oughly reduced to nitrite, the test giving a ‘dark red color in 6 
days. In culture 3 the dark color was not obtained till the 26th 
day, the test resulting in a faint color before that date. In cul- 
ture 6 no reduction was observable till the 14th day, and at the 
end of 28 days the test gave only a faint color. In cultures 4 
and 7 there was practically no reduction of the nitrate, the test 
only giving a trace of color at the end of 25 days. 
Color.—The normal appearance is a light yellow color of the 
mass of growth, accompanied by a fine pink tint throughout the 
medium. Where the species occurred abundantly in the air, a 
considerable difference was observable in the shade of yellow of 
the different colonies growing on a single plate, and this was 
also observable in the various cultures obtained. The color 
varies from nearly white to rather dark yellow. I have a cul- 
ture which has become entirely white from repeated cultivation, 
though retaining the pink tint apparently undiminished. There 
is also variation in the opacity of the growth. In culture 5. the 
yellow color was bright, but the pink tint scarcely perceptible. 
In 3, after cultivation for some months, the pink became very 
faint, though distinct at first. In culture 7, no pink tint was 
discernible when received, but after cultivation for some months 
it became quite well marked. In 6, the growth was white with 
a yellow tint only, but a fine pink color in the medium. 
‘T have considered all cultures to belong to Bacillus lactis 
erythrogenes that exhibited both the yellow and pink tints in 
some degree, and which liquefied gelatin, at least finally; but I 
possess cultures in which there is no pink tint discernible, some 
of which liquefy gelatin, and others not. Are these all’ good 
species or only slightly further varieties of Bacillus lactis 
erythrogenes? The forms may be tabulated thus, in regard to 
the most salient features : 
