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22 ACUTE POLIOMYELITIS the ganglion cells of the anterior horn. Strauss, by means of Bielschowsky's method, has recently shown atrophy to be the initial change in the intracellular network of the neurofibrillar. By the use of Nissl, Von Gieson and other methods of staining, the cell body has been proved to swell and to become more globular. With this swelling a disintegration of the Nissl granules occurs and often extends throughout the whole cell. If a section of such a swollen cell does not implicate the nucleus, the entire cell appears to be changed into a homogeneous anuclear structure, frequently without a single process. But serial sections usually demonstrate that this appearance is deceptive, for the nucleus and the cell pro- cesses can be found in contiguous sections. In many cases, the nucleus retains its normal appearance for a remarkably long time. Generally, it also conserves its normal position in the middle of the cell. When a severer change occurs in the cell body the nucleus is converted into a deeply staining, irregularly shaped structure. Sometimes complete karyolysis happens. Occasionally vacuoles in varying number are studied through the protoplasm.

The severity of the ganglion cell changes usually is in direct ratio to the intensity with which the interstitial tissue is affected. No nerve cells, as a rule, are visible, in the largest infiltrations, but slightly altered ganglion cells are sometimes present in the midst of a markedly infiltrated area. On the other hand, degenerated cells unaccompanied by interstitial changes have never yet been found in man. The interstitial changes do not necessarily consist of pronounced cell accumulation ; edema may prevail. Degenera- tion of the ganglion cells without inflammatory reaction occurred in a case of Cestano-Savini and Savini, but this particular case clinically as well as pathologically differed so widely from all others hitherto described, that I fully agree with Strauss that it was not a case of acute poliomyelitis.

Remarkably numerous neurophages were described by Forssner and Sjovall, who attributed to them considerable importance in the degeneration of nerve cells. In my later cases I have fully confirmed these observations. As shown in Plate I, Figs. 1-2, round cells invade and ingest the ganglion cells till only a clump of round cells with greatly increased protoplasm remains to mark the site of the ganglion cell. In this process the polynuclear leu- cocytes and the polyblasts are the chief, if not the sole, agents.