colonies of Bacillus anthracis, and then dried them under heat, noticing
that the rods and the spores would cease growing. When the rods were
placed back into the growth medium, nothing changed—they were
apparently inactivated and their contagiousness halted—and it was
obvious to Koch that the rods were not the robust form of the contagion.
On the other hand, the spores were resilient to temperature and dryness,
able to spring to life once placed back into culture, generating new rods
and spores capable of producing disease. This, he reasoned, was how
anthrax infected herbivores: in spore form it could reside in a field,
surviving years in suspended animation, waiting for invigoration in an
animal’s body. He had solved the life cycle puzzle of anthrax.
The Wöllstein physician and part-time scientist knew his work was
important, but isolated in his small Prussian town wasn’t sure with whom
he should liaise. Koch reached out to Ferdinand Cohn, who invited Koch to
Breslau to demonstrate his experiments. Within days, Koch “headed to the
train station carrying microscopes, slides, cows’ eyes, mouse spleens, and
boxes of rabbits, frogs, and mice—many, many mice, both living and dead.
Some were flush with anthrax. Rushing through the Wöllstein station to
make his train, laden with boxes and trunks, he must have been quite a
sight.”^36
When Koch arrived in Breslau, he immediately set up his equipment in
Cohn’s institute, inoculating animals and culturing eyeball fluid. In the
days that followed, scientists visited him, assaying his progress and taking
stock of his meticulous techniques. Soon, rods and spores were emanating
in media and animals were succumbing to disease. An esteemed professor,
Julius Cohnheim, the director of the Institute of Pathology and a former
assistant of Virchow’s in Berlin, came to survey the progress. Cohnheim
“couldn’t get over how methodical and thorough this Koch was; he
apparently emerged from nowhere but was calmly demonstrating the most
deliberate and decisive laboratory techniques Cohnheim had ever seen.”^37
Professor Cohnheim, dazzled, departed from the makeshift
experimental setup and rushed across campus to his assistants, telling
them to stop what they were doing and to get over to Cohn’s lab to witness
what the wunderkind was demonstrating. He said, “I regard it as the
greatest discovery ever made with bacteria and I believe that this is not the
last time that this young Robert Koch will surprise and shame us by the
brilliance of his investigations.”^38