36 
Growth of Bacilli 
In the later stages however the disturbance caused by one organism 
snapping moves a number of others and alters the relative positions of 
the members of the group. 
In Fig. 9 (x about 300) two curved bacilli are seen. The upper 
one subsequently undergoes no change, but the lower bacillus gives 
rise to a small colony. Fig. 10 (115 minutes) represents the condition 
seen shortly after the division of the lower bacillus, and Fig. 11 (130 
minutes) illustrates the approximation of the distal ends of the new 
rods resulting from further growth. Fig. 12 (240 minutes) shows a 
small colony of seven individuals formed from the lower bacillus. The 
upper bacillus is straighter than in the earlier photographs, but this 
change is probably due to pressure on its lower end produced by contact 
with one of the newly formed organisms. 
Fig. 13 illustrates the condition of a suitable field at an early 
stage of development (55 minutes after the observations commenced). 
Single bacilli or pairs of bacilli, developed from single individuals, are 
scattered over the field. Fig. 14 shows the same field after six hours’ 
growth. Here seven large colonies are seen. Four (A, C, E, G) have 
Diagram 5. Illustrating the development of B, diphtheriae on the surface of agai. 
