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March 1, 1941


JAMA. 1941;116(9):839-840. doi:10.1001/jama.1941.02820090039012

The close resemblance between human poliomyelitis and spontaneous encephalomyelitis in mice enhances the value of recent contributions to the epidemiology of this veterinary disease. Seven years ago Theiler1 found an occasional young mouse with flaccid paralysis of the hind legs among the stock mice purchased by his laboratory. Stock mice similarly affected have subsequently been described by numerous European and Asiatic investigators,2 an average of about one purchased mouse in 3,000 exhibiting this disease. Five strains of the specific neurotropic virus responsible for this paralysis have been isolated by Theiler and propagated by brain to brain inoculation.

In mice injected intracerebrally with this isolated virus the first sign of the infection is almost invariably a weakness of one of the fore limbs, which usually develops after an incubation period varying from seven to thirty days. This weakness is progressive, rapidly changing to a flaccid paralysis and almost invariably