GENERAL CHARACTERS OF BACTERIA. 
II 
short ones, with only a single turn (Fig. 7, c). This type is of less 
importance than the others. 
Motility of Bacteria. The next point of distinction among 
bacteria is based upon their motility. Some bacteria are capable 
of an active swimming motion, others are stationary. The motion 
is produced by minute, extremely delicate, vibrating hairs, called 
FIG. 7. General shape of bacteria, a, spheres; b, rods; c, spirals. 
flagella (Fig. 8). The flagella are so delicate that they cannot often 
be seen in the living bacteria, and they do not stain by the ordinary 
method of staining. Therefore, they are never seen in the usual 
microscopic preparations. They may be seen by special methods, 
but these are so difficult that the beginner cannot use them satisfac- 
torily. The question of their motility is, however, usually determ- 
FIG. 8. Showing bacteria with flagella; a, peritrichic; b, lophotrichic; c, monotrichic. 
ined without staining, by the study of the living bacteria (Experiment 
No. 8). These flagella are differently distributed upon different 
bacteria. Sometimes there is a single one on the end of a rod 
(Fig. 8, c) monotrichic; sometimes a small tuft at one or both ends 
of a rod (Fig. 8, b) lophotrichic; and sometimes there is a cover- 
ing of flagella over the whole body of the bacterium (Fig. 4, a) 
peritrichic. 
