poison spread to any extent, from the area first attacked, so that the characteristic appearances of acute poliomyelitis later develop, although the lesion in the primary disease focus in the cord be due to an infection by way of the blood, the subsequent and typical lesions certainly are not.
Leiner and v. Wiesner state that in monkeys, inoculation of the blood only exceptionally is successful. They have never, during the incubation period, been able to demonstrate the presence of the virus in the blood. Their observations sharply contrast with those of Krause and Meinicke who, as I have mentioned, state that in rabbits the most effective site of inoculation is the blood and who have demonstrated the virus in the blood, as well as in other tissues, during the initial stage of the disease.
Harbitz and Scheel arrive at a conclusion similar to my own, except that they maintain that the virus reaches the pia by way of the blood, and then invades the spinal cord along the sheaths of the vessel. Fr. Schultze, indeed, had already dwelt upon this possibility. He, however, considered it as an accidental phenomenon, which might happen in the course of a cerebrospinal meningitis, and which infrequently afforded an explanation of the characteristic pathologic picture, or of the symptom complex of the disease. Leiner and v. Wiesner, while not clearly recognizing the principal point of the problem—the peculiar localization, with marked participation of the gray matter, especially in the anterior horn—yet acknowledged the lymphatic origin of the morbid changes in the nerve substance. The double step in the infection seems to me not very probable; and microscopical examination fails to substantiate that the inflammation, as a rule, diffuses inward from the pia.
The point at which the virus enters human beings is still to be determined. Many different sites have been incriminated; e. g., because of diarrhea in the initial stage, the alimentary canal was accused; because of angina, the throat; and because of bronchitis, the respiratory tract. Experimental research, especially by Römer and Joseph, proved that diarrhea might occur after intracerebral infection. Diarrhea, angina and bronchitis may, therefore, be accepted as consequent upon the elimination, and not upon the invasion of the virus. If it be permissible to deduce from animal experiments the mechanism of morbid changes in
