evident not only in the different epidemics; not only in the various foci of the same epidemic; but also even in the different cases within a single focus. Its protean character may be gathered from the reports of different observers. Thus, one observer sees none but the typical; while another, of mature experience, reports a number of atypical cases. I can refer to no better examples than Medin, Nonne and Spieler, who, according to present ideas, had at their disposal very scanty material and yet recorded unusual forms.
Later I shall also show that the prognosis of sporadic acute poliomyelitis and that of epidemic acute poliomyelitis differ relatively less than was formerly alleged; and that the epidemic behavior is in no way distinctive, as was shown by my observations upon the Swedish epidemic, and presents all possible degrees from apparently isolated sporadic to accumulated and more or less pronounced epidemic cases. The map of the distribution of acute poliomyelitis in the Swedish outbreak shows that the disease occurred in foci, within each of which usually a continuity of spread could be demonstrated. Such was the case in those parts of the country in which the disease appeared not in epidemic form but only as isolated sporadic cases. From what I have said there can be little doubt that epidemic and sporadic poliomyelitis are one and the same disease.
Etiology.—Infantile paralysis has from earliest times been attributed to a variety of causes; e. g., trauma, cold, teething, etc. Infectious diseases, such as scarlet fever, measles, and pneumonia, rarely were alleged to be the cause, and a belief arose that under certain circumstances their toxins could produce infantile paralysis.
In 1887, Strumpell—and later Pierre Marie—stated that infantile paralysis was a disease per se, independent of other infectious maladies. Experimental research and the study of epidemics have since adequately confirmed this statement. Naturally, a specific organism was early sought but as none was found either in cultures or in spinal cord sections, the morbid changes were attributed to the action of a toxin. During the last decade several microorganisms from the spinal fluid in this disease have been announced. Fr. Schultze, Concetti, Looft, Dethloff and others whose examinations were restricted to single cases, and Geirsvold and Potpeschnigg who investigated large series, all reported such
