In two out of three large urban epidemics of poliomyelitis the virus of this disease has been detected in samples of sewage. From one of the sites it was found repeatedly. Both positive sites were located in the vicinity of isolation hospitals, and we believe that the findings indicate that this virus can be transported, for short distances at least, through the medium of flowing sewage.

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Since the early days of the discovery of the virus of poliomyelitis it has been known that quantitative differences in virulence for the monkey exist between recently isolated strains, and strains which have passed through successive monkeys. Only within the last few years has it been clearly demonstrated b y the work of Burnet and Macnamara (1) in Australia, that immunologic differences exist between such strains, which might be termed qualitative differences, in that they do not seem to be confined to those of virulence alone.These investigators made a comparative study of two strains; one a local virus recently isolated from a fatal human case, and the other the Rockefeller Institute strain of so called mixed virus (M. V.). They described three instances in which monkeys contracted a fatal attack of poliomyelitis following the intracerebral inoculation of the M. V. strain despite the fact that some weeks previously the monkeys had sustained a typical attack of poliomyelitis produced by the local strain. The reverse of this experiment was also demonstrated in a single instance, in which a recovered monkey, partially paralyzed by the M. V. strain, was subsequently brought down with complete paralysis by the local virus. Furthermore, they found in neutralization tests that, although pooled convalescent serum would neutralize both strains, a few tests with individual samples of convalescent sera failed to show this parallelism, in that only the local virus was neutralized.In corroboration of this work Weyer (2) later described differences in the neutralizing values of human convalescent and antiviral horse serum for recently isolated strains and for a monkey passage strain. Flexner (3) has also pointed out that immune sera prepared from "human" and old passage strains of virus * The expenses of this investigation were defrayed by several grants from: (a) the Fluid Research Fund, Yale University; (b) an anonymous donor; and (c) the 1932 Philadelphia Poliomyelitis Fund. 513

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