Page:Acute Poliomyelitis.djvu/15

 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. Meinecke explains most of the negative results of other experimenters on the grounds of variation in the susceptibility of different breeds of rabbits and of insufficiency in the amount of the infective material injected. 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.

The clinical picture of monkey poliomyelitis corresponds very closely to that in man. 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. According to these observers the incubation period, from the injection until the onset of paralysis, is 9-10 days; its minimum is 4, and its maximum 33 days.

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. Examination of sections of human and of monkey's tissues and the study of the cerebrospinal fluid, blood, etc., by every conceivable method have given uniformly negative results.