G. S. Giuiiam-Smitii 
35 
the rod; sometimes more than one such segmentation line is visible in 
a single rod.” Usually however no such changes can be made out and 
without warning there is a sudden snapping across of the rod resulting 
in the two portions lying at an angle with each other. “ Subsequent 
growth results in the gradual approximation of the distal ends of these 
two rods to each other giving a more or less parallel arrangement. The 
proximal ends of the new rods (those which before snapping were 
continuous with each other) remain contiguous to each other after 
parallelism is achieved. In such movements one or both rods necessarily 
describe parts of a circle, and when, as often happens, the two I’ods are 
not of the same length, the shorter usually moves through a much 
greater arc than the longer. Subsequent growth does not usually 
result in the separation of the two portions at the proximal ends, the 
increase in length in the larger portion apparently carrying the other 
portion with it. That something unites the proximal ends seems to be 
further evident because if two rods thus derived be disturbed, as by 
a current of water, so that they drift off, turning over and over, their 
relative positions remain unaltered. A single rod may break up into 
three portions instead of two.” 
After a period of further growth the two newly formed rods again 
divide in the same way. The continuation of this process gives rise 
to the peculiarly arranged Chinese letter like groups of bacilli so 
characteristic of the diphtheria group. 
Plate VI, Figs. 1 to 8 (x 100) illustrate the changes undergone by 
three diphtheria bacilli. In the left hand specimen in figure 1 a single 
division has already taken place and the two new organisms are disposed 
at nearly a right angle to each other. The central organism has also 
just divided, while the right hand one has not. In Fig. 2 (55 minutes) 
the two bacilli on the left have again divided, producing a colony of 
four bacilli disposed at various angles to each other, and considerable 
growth has occurred in the central specimen. In Fig. 3 (95 minutes) 
further growth has occurred in the central and left hand specimens. 
In the latter the distal ends of the organisms formed during the last 
division are beginning to approach one another. The right hand 
specimen has now divided. In Figs. 4, 5 and 6 (125, 180 and 280 
minutes) multiplication by similar divisions can be followed until three 
separate colonies are seen in Fig. 7 (315 minutes). The very consider¬ 
able variations in size of the component bacilli are clearly shown. In 
Fig. 8 (370 minutes) the three colonies have coalesced. 
During the earlier stages of growth such as are seen in Figs 1. to 5 
“ snapping” in one bacillus does not influence the others to any extent. 
3—2 
