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24 ACUTE POLIOMYELITIS ganglion cells will be detected. Strauss has since confirmed these observations.

In general, the nerve filaments of the gray matter are faintly stained and of irregular contour. Sometimes they show little swollen nodes like a chain of pearls ; usually they are degenerated ; sometimes only fragments can be recognized.

The parenchymatous changes in the posterior are analogous to, but not so marked as, those in the anterior horn. The differ- ence lies in the slighter interstitial changes and the lesser implication of the nerve cells in the posterior horn.

In the region of the central canal, Wickman observed round cells, which in places penetrated between the ependyma cells ; but the evidence of inflammation in this neighborhood was scanty.

In the bundles of white nerve fibers round cell accumulations are few and contain no nerve filaments. The changes in the white matter are very slight, and are due chiefly to edema. Swelling of individual axis cylinders has been noted ; but with Weigert's method, at least in my cases, only imperfect staining was demon- strable. Rissler observed degeneration and tortuosity of the axis cylinder. In the acute stage, the changes in the posterior and anterior roots are very mild: they consist chiefly of the invasion of'the fasciculi of the anterior root by the pial exudate penetrat- ing between the nerve fibers. The vessels of the roots may also be infiltrated. Enlarged axis cylinders in the anterior and posterior horns have been observed. Siemerling found that the Marchi stain produced an appearance of black dots in the extramedullary portion of the anterior and posterior roots. Redlich and Moncke- berg described degenerative changes in the peripheral nerves. As these changes were slight, and as no evidence of local inflamma- tion was observed, the degeneration must be considered as secon- dary. This secondary degeneration is not often present.

Forssner and Sjovall were the first to examine the cells of the intervertebral ganglia. They were able to prove inflammatory changes. Their observations were later confirmed by Marburg and Strauss, but Harbitz and Scheel found the ganglion cells normal.

Microscopic examination of the spinal cord has "not yet re- vealed bacteria. Bonhoff, however, has demonstrated, by Mann's method, nuclear enclosures in the neuroglia cells, which he believes to be foreign bodies of a specific nature.