still less by rounded protozoa, which
are much larger than microbes and soft in substance. This well-known
and clearly demonstrated fact ought to have suggested a problem to the
minds of students: How do the protozoa of malaria enter the
circulatory current of the blood? But ever since the days of
Hippocrates, Pliny, Celsius and Galen it had been held that this fever
was caused by the "poisonous atmosphere" of marsh lands, the bad air
of the morning and the evening, so much so that even a few years
before the discovery of the real cause of malaria, eucalyptus trees
were planted in the belief that they would filter and disinfect the
air. How was it that no one asked himself how it was possible that the
plasmodia could enter the _current of the blood_ from the _air_? What
was the species of torpor which took possession of the intelligence of
persons who had specialized in intellectual work? Here was a colossal
_sum_ of intelligence, without any individuality.

Until Ross discovered that birds are inoculated with malaria by a
particular kind of mosquito.

And then, behold! we have at last the fundamental argument from which
the knowledge of the truth sprang forth: "If birds are inoculated with
malaria by mosquitoes, then the same thing must happen to man."

A simple argument, which sped like an arrow to the final discovery.
Nothing seemed more _incredible_ than the fact that in the malarial
regions good air and fertile soil were to be found, that it was
possible to breathe that air morning and evening and remain in perfect
health, so long as one was not bitten by mosquitoes, and that the
innumerable peasants who were wasted by malarial anemia would be saved
and restored if they protected themselves by mosquito-netting. But
after the first stupefaction, when men were convinced of the facts,
there was an outcry from all the intelligent: How was it possible that
we did not find it out before? Was not the cycle of the protozoa a
well-known fact? Did not every one declare that the system of
circulation was closed and impervious to micro-organisms? Was it not
natural to think that only a blood-sucking insect could innoculate it?

How many students _felt_ that glory had passed close to them, and were
amazed and saddened by the knowledge, like the disciples of Emmaeus,
who said to each other when the Master disappeared before they
recognized Him: "Did not our hearts burn within us when He spoke and
expounded the Scriptures to