Ivan Wickman

“ Even to drying, the virus is most resistant. The experiments of Leiner and von Wiesner show, however, that if the virus be allowed to dry in thin layers of infected tissues, if it be allowed to desiccate therefore under conditions which approximate to actual experience, it rapidly decreases in virulence. The poison is more sensitive to high than to low temperatures. ”

“ Thus, Flexner and Lewis—who have done most work in this field—failed in numerous experiments to cause the disease by intracerebral inoculation of guinea pigs, rabbits, horses, calves, goats, pigs, sheep, rats, mice, dogs, and cats. Most observers have found animals other than monkeys to be refractory, But Krause and Meinecke, also Lentz and Huntemuller, have reported as many successful transmissions in rabbits by inoculation through the blood stream, as in monkeys by intraspinal inoculation. Insignificant pathologic-anatomic changes were found in the spinal cord of the rabbits. ”

“ The most important distinctions are the absence in monkeys of the initial fever, and the frequency with which the disease is characterized throughout its course in them by subnormal temperature. Prodromal symptoms sometimes usher in the paralysis but are often absent. The paralytic signs develop in rapid succession. The brunt of the attack falls upon the legs; and a flaccid paralysis develops which is characterized by atrophy and loss of reflexes. The mortality among monkeys is very high. In Flexner and Lewis' experiments the death rate among 81 monkeys was 54.3 per cent. ”

“ The virus occurs in the spinal cord. By injecting virulent material into the brain the spinal cord is made virulent and we can then reproduce the disease in monkeys by intracerebral inoculation with this virulent spinal cord tissue. The virus has thus been propagated through many generations of monkeys. ”

“ These features are, however, negligible factors in monkeys in which a minimal dose suffices to produce the disease. It seems to me, with so many contradictory statements about poliomyelitis in rabbits, that until we have further information only monkeys should be used for clinical research purposes, for failure to reproduce the disease by inoculation is in them exceptional. ”

“ Celebrated writers have even stated that acute poliomyelitis does not occur in adults. But the statistics of Wickman and Leegaard, however, show that adults are by no means immune. Fr. Schultze, Rissler, Taylor, van Gehuchten, Wickman and others had already by pathologic anatomic examinations proved that the disease affects adults. Wickman saw a man of 46 years suffering from a typical attack, while his nine children living in the same house with him remained unaffected. It is possible that conditions change from epidemic to epidemic, so that the frequency of attacks upon adults varies. ”

“ The pathologic-anatomic picture—apart from the results of Leiner and von Wiesner—corresponds with that which we find in man. The most important results yielded by experimental investigation are, however, those which relate to etiology and pathogenesis. ”