30 
Growth of Bacilli 
or slightly carved chain composed of three, four or more distinct rods is 
produced. As growth progresses and more rods are formed the chain no 
longer remains straight or slightly curved, but develops angles at the 
points of junction of the various bacilli. These angles rapidly become 
more and more marked so that the chain exhibits a folded or zigzag 
appearance. By the further development of the folding process many of 
the rods come to lie parallel with each other, often with their long axes 
at right angles to the direction of the original chain. Continued growth 
then gives rise to the development of strands of parallel chains of 
bacilli, which ultimately become curved and wavy. Irregularities in 
the folding process not infrequently produce distorted loops. 
The development of a bacillus belonging to this group on the 
surface of agar is illustrated in Plate V. Fig. 1 (x 250) shows a 
single, slightly curved bacillus. At its lower end a thinner pale 
prolongation is seen. This either represents an empty portion of the 
capsule or perhaps a dead bacillus. It is evidently incapable of growth 
and can be traced in exactly the same condition for 170 minutes 
(Figs. 1 to 6). Fig. 2 (75 minutes) shows an increase in length. 
Three bacilli are now seen, the lower two forming a slight angle with 
each other, and the third joined to the upper of the two at a greater 
angle by a faint connection, like the prolongation seen in Fig. 1. As 
in the former case no growth occurs in this region, which can be traced 
up to Fig. 6. The fact that its diameter greatly diminishes (Figs. 
4 to 6) seems to confirm the view that it represents a stretched portion 
of capsule. In Fig. 3 (95 minutes) further growth has occurred, the 
two adjacent bacilli having divided into four, which lie at a small angle 
with each other, and the upper one having divided and formed a chain 
of two individuals, whose long axis is now disposed nearly at right 
angles to that of the main chain. Fig. 4 (125 minutes) shows the 
commencement of the folding process. The main chain has divided 
into seven individuals, and the angles formed at the junctions of the 
upper three and the lower three are very marked. In Fig. 5 (150 
minutes) the main chain consists of thirteen individuals. The parallel 
arrangement produced in its upper and lower portions by the continua¬ 
tion of the folding process, resulting in the complete approximation of 
the bacilli forming the angles, is well seen. In Fig. 6 (170 minutes) 
the increase in the number of the bacilli forming the chain is well 
shown, and parallelism is a marked feature. This figure also illustrates 
the formation of angular loops, which are marked features in the peri¬ 
pheral portions of some colonies of organisms belonging to this group. 
