The Spirillum is a long, well-marked spiral; the Spirochaete is similar (Fig. 198, D 3).
The Vibrio (Fig. 198) is a variety of the spirillum, and is a rod-shaped, jointed organ ism, presenting undulations, but not the marked cork-screw appearance of the spirillum.
All of these, we have seen, multiply by one of two ways, either by division or by the forma tion of spores, but the rapidity of their increase is beyond conception. In one brief hour, under favourable conditions, one may perceive the whole progress of their life-history. Here is a comparatively simple calculation, but one whose remits are so normous that the authority of one of the most distinguished of investigators is given for its accuracy, that of Prof. Ferdinand Cohn of Breslau. ()liven that one bacterium will divide into two in one hour, then each of these two in another hour will divide, making 4, after three hours there are 8, and so on. At the end of 24 hours, from one bacterium there are developed 16i millions (16,777,216). After
48 hours the number amounts to 281i billions, and after 3 days to 47 trillions. Into a flask containing a clear, transparent, organic fluid, and under favourable conditions, sow a drop of water containing but one bacterium, and such as this is the result. Nevertheless the multi plication is not indefinite; it is indeed strictly limited. It is from the contents of the organic solution that the bacteria obtain the nourish ment for their life and growth. Aa soon as they have exhausted the nutriment, they can no longer multiply, and will speedily cease to exist.
Accompanying their multiplication changes take place in the clear fluid which are quite visible to the naked eye. It becomes muddy, turbid, and loses its transparency. When the bacteria have exhausted the nourishing ma terial, they fall to the bottom as a deposit, and the fluid may become again quite clear, but altered in constitution, because its complex con stituent; have been rent asunder to supply food to the organisms.