November 22, 1912] 



SCIENCE 



687 



ploitation under laboratory conditions. It 

 is obvious that the more nicely a parasitic 

 organism is adjusted to its host the more 

 difficult it will be to cultivate it outside 

 the host and the more quickly it will lose 

 in culture its pathogenic power. The pal- 

 lidum, which for so long resisted the efforts 

 to transmit it artificially to animals and 

 then to cultivate it outside in vitro, loses 

 after a few generations, as was to be ex- 

 pected, its disease-producing virulence, 

 while the blood parasites of relapsing and 

 tick fevers in man and spirillosis in fowls, 

 which are strictly parasitic and pass a 

 stage of their life in biting insects, retain 

 this power for many generations. In turn, 

 the culture of the pallida has yielded 

 luetin which by causing a local allergic or 

 hypersensitive skin reaction has provided 

 clinical medicine with a new means of de- 

 tecting latent luetic infection. 



With this introduction to the more gen- 

 eral theme of the hour I shall invite you to 

 follow with me somewhat minutely the bio- 

 logical investigations of a disease that is 

 still claiming the absorbed attention of 

 both physicians and people, namely, polio- 

 myelitis, or infantile paralysis. The dis- 

 ease has just been making the rounds of the 

 world, coming as a very unwelcome in- 

 truder to many different countries. Until 

 the present pandemic it was surrounded 

 with mystery and fortified by superstition. 

 It is the story of the working out of the 

 natural history of poliomyelitis, now eluci- 

 dated in many ways, that I propose to tell 

 you. I have been led to choose this par- 

 ticular disease as my theme, both because 

 it has claimed much of my attention dur- 

 ing the past several years, and because it 

 illustrates admirably certain general 

 truths to which I desire to call your atten- 

 tion. 



Poliomyelitis has been endemic in north- 

 ern Europe for many years, but it is only 



five years since it started on that unique, 

 and as yet unexplained, movement that has 

 carried it around the globe. In America 

 there is no previous history of a general 

 prevalence or epidemic, although local out- 

 breaks of infantile paralysis have from 

 time to time arisen. Some significance at- 

 taches to the fact that the first two foci of 

 the present epidemic — I say present, be- 

 cause since 1907 the disease has prevailed 

 severely each summer and autumn at some 

 places in the United States and Canada — 

 arose in the Atlantic coast cities and in 

 the state of Minnesota in the middle west. 

 The former receive the mass of emigrant 

 population from Europe, and the latter, 

 secondarily, the large contingent of Scan- 

 dinavian emigrants. The imposition of the 

 infection upon America can thus be ac- 

 counted for ; but no explanation is afforded 

 of the many years of immunity while 

 Scandinavians were constantly arriving, 

 and for the penetration of the disease to 

 other European countries and to far dis- 

 tant parts of the world. However, within 

 the pandemic period the disease has taken 

 on new activity in Norway and Sweden, 

 and as recently as 1911 the latter country 

 has suffered a severe visitation. 



On clinical grounds Scandinavian ob- 

 servers'' had recognized the essentially in- 

 fectious nature of poliomyelitis and had 

 followed the evolution of the outbreaks and 

 traced the connection between many of the 

 cases. They became the defenders of the 

 notion of human carriage, and by estab- 

 lishing certain unusual clinical forms of 

 the disease— such as meningeal and abor- 

 tive — placed this idea on firm ground. The 

 notion was further extended to include 

 healthy carriers of the infection who act 

 as intermediaries between the actively ill 

 and the new victims of infection. These 



' Wickman, ' ' Beitriige zur Kenntnis der Heine- 

 Medinsehen Krankheit," Berlin, 1907. 



