26 
Growth of Bacilli 
early formation of loops in the central portion of the chain is also seen. 
On the portion of the chain extending to the right a small angle may 
be noticed. The smaller bacillus is partly following the curves of the 
larger. Fig. 4 (170 minutes) shows increased growth and increased 
loop formation. The angle noticed on the right portion of the chain 
has now developed into a process and a loop is in the process of forma¬ 
tion. Fig. 5 (215 minutes) illustrates a further advance in loop 
formation and the development of parallel strands of bacilli. Both 
the right and the left ends of the chain are now seen to be producing 
secondary systems of loops. Fig. 6 (292 minutes) illustrates a more 
advanced condition of the central portion of the colony. Parallelism 
is well marked and numerous loops are seen. The rapidly developing 
secondary system of loops on the left end of the chain is well shown. 
Fig. 7 (x 100) is a photograph of the complete colony after seven 
hours’ growth. The primary system of loops is well shown in the 
middle and close to it on each side the secondary systems formed on 
the two ends of the chain. The two free ends are seen extending 
downwards. Above each of these is a less curved apparently freely 
projecting thread. These are in reality processes composed of parallel 
threads of bacilli produced in the same way as the process in Fig. 3. 
Fig. 8 illustrates the same colony after 23 hours’ cultivation. Growth 
has mainly occurred in the central portions of the colony resulting in 
the production of very numerous loops, and large numbers of strands of 
parallel threads of bacilli. Moreover the whole colony is not now on 
the same plane as increased growth in the centre has caused some 
strands to override others. 
In this series of photographs the formation of a complete colony 
is illustrated almost from the commencement of growth to the formation 
of a typical anthrax colony consisting of a raised centre of wavy strands 
surrounded by numerous loops and a few projecting threads. 
The development of such a colony has been followed on many 
occasions and complete division of the original chain has very seldom 
been noticed. Occasionally, however, this does occur after an acute 
angle has been formed. It may therefore be stated as a general rule 
that a superficial anthrax colony consists of a single twisted chain of 
bacilli. 
In the depth of the agar as on the surface a chain of closely 
approximated bacilli is first produced. As the chain grows it becomes 
irregularly curved; but owing to the resistance of the agar regular 
loops cannot be produced, and instead distorted loops, which may be 
