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Rh be very marked, although, as a rule, it is slight. Among such conditions, extreme virulence of the infection ranks first.

It would not be surprising if an increase of virulence influenced the toxic peculiarities of the virus. Such a circumstance, however, can hardly affect our conception of the nature of the changes. Probably passage from monkey to monkey enhances the virulence.

Most recent investigators believe the changes in acute poliomyelitis to be inflammatory. Goldscheider, Redlich, Bülow-Hansen and Harbitz, Wickman, Harbitz and Scheel, Benecke, and others regard the degeneration of the ganglion cells as a special consequence of the interstitial inflammation. Ernst, Schwalbe, and others consider the parenchymatous and interstitial changes as synchronous. Many pathologists, however, believe that here, as elsewhere, it is immaterial whether an inflammation is discernible first in the parenchyma or not. The essential points to be determined in either case are the same: First, why the malady, which from a pathological standpoint is a strictly localized affection, develops clinically as a systemic disease; and, second, why the effects are limited practically to the anterior horn, and are not distributed as in a transverse myelitis.

Pierre Marie thought that Kady's experiments upon vascular distribution in the spinal cord solved the whole problem. Kady proved that the anterior horns are supplied from the central artery which, at the bottom of the anterior fissure, enters the spinal cord and turns forward to ramify within a restricted zone. Pierre Marie supposed the morbid process to consist of embolism or of thrombosis of the central artery. His theory received some support from the experiments of Hoche and Marinesco. It was generally accepted. I, however, felt compelled to raise the following objection to it:

1. In recent cases, neither embolic nor thrombotic processes have been demonstrated. Mott, Money and Batten have, it is true, each reported a case where thrombosis was present. But the most recent of these cases had already lasted thirteen days and such thrombosis may better be interpreted as a secondary process. In more recent cases, in spite of eager searching, thrombosis has not been found. And the isolated observations just reported are totally inadequate to permit a generalization.

2. The changes in Heine-Medin's disease are radically different