ON SOME NEW MICRO-ORGANISMS OBTAINED FROM AIR. 
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In the first place there are compact colonies in the depth of the gelatine, which 
soon show small spinose or hair-like extensions from the periphery. These extensions 
increase in thickness, but remain fairly uniform in length, and ultimately the colony 
produces a liquid circle in the gelatine, and the periphery of this circle has also a 
finely spinose appearance. This appears to be the only form of colony which has 
oeen described by other observers. The appearance of these colonies may be compared 
to that of a “ crown of thorns.” 
In a modification of the first class of colony, which appears to arise when the plates 
are incubated at a somewhat higher temperature, the hair-like extensions from the com¬ 
pact colony in the depth are much longer and irregular, often spiral and twisted, or 
resembling the lash of a whip. The formation of these longer extensions is probably 
accounted for by the smaller resistance offered by the gelatine at the higher temperature. 
These likewise ultimately produce liquefied colonies which do not differ in appearance 
from the liquefied colonies of the first class. This second class may be designated 
whip-colonies. These whip-like colonies appear to be especially characteristic of 
Bacillus cereus. (See Plate 20, fig. 3, No. 3c.) 
Thirdly, there are found surface-growths of very remarkable appearance, and 
consisting of parallel bands of threads meandering over the surface of the gelatine in 
the most capricious maimer, and frequently expanding into coils. These surface- 
growths are often quite independent of any compact colony, their production being, as 
far as we can see, due to the original individual organism or group of organisms from 
which they have sprung being situated so near the surface of the gelatine that the first 
out-growth, having promptly reached the surface, has there grown out in free contact 
with the air with enormous rapidity. Thus in very young plates these surface-growths 
are already found of enormous dimensions compared with the compact colonies in the 
lower strata of the gelatine. This third class may be fitly named meander-colonies. 
They also give rise to liquefaction, the edge of the liquefied portion being similar to 
that of the liquefied colonies of the other two classes. We have found these meander- 
colonies in the case of the Bacillus cereus as well as in that of Bacillus subtilis. 
In Plate 20, fig. 4, we have represented a colony of the Bacillus anthracis which 
presents many points of resemblance to those of the Bacillus subtilis, more especially 
to the “ whip ” and “ meander ” modifications. 
Points of Distinction between B. lsevis, B. cereus, and B. subtilis. 
From the descriptions which we have given above it will be seen that these three 
micro-organisms resemble each other very closely in many points; they can, however, 
be sharply distinguished on the following grounds :— 
Liquefaction of gelatine. — B. cereus causes by far the most rapid liquefaction of 
the gelatine ; B. subtilis stands second in this respect, the liquefaction being very 
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