Moreover, we are astonished by something still more serious: how came it that hundreds and thousands of students throughout the world accepted Laveran's error with their eyes shut, that not one among so many took into consideration on his own account the cycle of the protozoa, and that not one was sufficiently independent to set about studying the phenomenon for himself? What is this mental form of inertia? and why does it produce itself in man? All these disciples, heedless of the problem presented to their minds by the sexual form of the plasmodium, left it alone, although it had not yet been solved, and certainly had no intuition of the fame, the progress in science, and the benefit to humanity which would have been the outcome, had the problem constituted an obstacle which had arrested their attention, saying: "Solve me." They passed on indifferently, commending Laveran's "effort of genius," repeating with him: They are degenerate forms. A futile effort, which only increased a crowd of persons who had resigned their own individuality all unconsciously. Another biological acquisition was the assurance that the circulatory system of the blood is a closed system of vessels, and that the enclosing epithelium is not permeable by non-incisive solid bodies such as vegetable microbes, and 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."