42 Microbes and You 



For hours he watched intently to see whether these rods under 

 his microscope changed their size or their shape, but nothing 

 happened. Then suddenly he was able to observe that the rods 

 were becoming longer, and these elongated forms eventually broke 

 in half and formed two short rods. These short rods in turn 

 lengthened and subdivided by splitting in the very center, until 

 within a few more hours he had many times the number of organ- 

 isms that he started out with in his ox-eye fluid medium. This 

 was trulv an astounding discovery. Here was an organism probably 

 one-billionth the size of a sheep. Bv gaining access to the internal 

 organs of a sheep, the microbe could set up housekeeping, settle 

 down, and have a family within a relatively few minutes, and 

 before a single day had passed, untold numbers of offspring could 

 point with pride to their parent who came over on a blade of grass. 

 The multiplication of rabbits is put to shame when compared 

 with the ability of bacteria to reproduce several times during a 

 single hour! When these overwhelming hordes of microorganisms 

 had parasitized enough cells of the sheep, the afflicted animal could 

 no longer overcome their deadlv eftect, and the sheep succumbed. 



After growing these bacteria away from the originally infected 

 sheep for generation after generation, would the far-removed off- 

 spring be able to establish themselves once more in the species of 

 animal from whence they originated in his experiments? This was 

 most important for Koch to know, and he promptly set about to 

 find the answer. He still had some of the mice he had killed with 

 blood-soaked splinters dipped in the juices of previously sacrificed 

 mice. It had been weeks since these offspring of the original 

 anthrax bacteria had been near sheep. If he could inject some 

 infected mouse blood back into sheep and have the larcrer animal 

 contract the disease, he felt that he could say with assurance that 

 these microbes were the cause of anthrax. As he hoped, the sheep 

 died with typical clinical symptoms of the disease. Not wanting 

 to shout from the housetops that he had solved the problem, Koch 

 very cautiously sent out feelers by casually telling some of his 

 intimate friends and colleagues what he had done. The)^ naturallv 

 raised questions which he could not always answer to their satis- 



