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18 and, as far as I know, all other investigators have similarly failed. Mott and Batten have each reported thrombosis in a single case. These cases, however, were respectively of 17 and 13 days' duration, and I believe it was a secondary phenomenon. Tiny hemorrhages in conjunction with the hyperemia occur not only in severely affected areas, but also in areas which otherwise show but little change. These hemorrhages are partly attributable to the inflammatory process. They may, however, partly be agonal changes, dependent upon the terminal respiratory paralysis. Siemerling's case showed, both in the lumbar and cervical regions, an extensive hemorrhage, which implicated the greater part of the anterior horn.

Hemorrhages are occasionally seen in the anterior horn, which explain the quite apoplectic type of paralysis sometimes observed. Motor disturbances may, however, develop with extreme rapidity solely from the inflammatory process.

More important than the hyperemia and hemorrhage is undoubtedly the cellular exudate. The cells are derived partly from the vessels and partly from the tissues. The first is the more constant source and in some sections the cellular exudate from the vessels is the only, or, at least, the principal pathologic change. (Plate II, No. 5.) The round cells which compose the exudate (in Fig. 11, No. 5) are situated in the adventitial lymph spaces of the vessel wall.

The infiltration of the adventitia is most marked around the entrance of the central vessels into the spinal cord at the bottom of the anterior fissure, where it is directly continuous with the infiltration of the pia.

It has been stated that the arteria centralis is the most severely implicated. But Wickman maintains that in his cases, so far as any difference in severity existed, the veins were more gravely affected than the arteries. Between the central and the peripheral vascular systems, with the exception of the severity with which the larger central vessels tend to be affected soon after entering the spinal cord, no evidence of any discrimination exists. Harbitz and Scheel, and Strauss also state that the veins are the more affected. Marburg, on the contrary, in his recent report of his cases, states that even at the very onset of the disease, the anterior horn shows dense infiltration around the arteria centralis. In rare