ACTIVE IMMUNIZATION 173 



and experimentally, is the predisposing influence to infection of 

 the continued use of alcohol and various narcotics. Of the manner 

 in which these agencies bring about the greater susceptibility to 

 infection nothing was known in the past, and even now our knowl- 

 edge is but imperfect. But we can at least suggest certain possi- 

 bilities. As we know that phagocytic action represents one of the 

 most important factors in our first line of defence, and as this has 

 been shown to depend to a very great extent upon the presence of 

 opsonins and tropins, it would seem reasonable to suppose that the 

 harmful agencies just referred to might readily operate through 

 interference with the production of such bodies as are essential to 

 phagocytosis. 



In this connection it is interesting to note that during pregnancy 

 which has long been recognized as a factor predisposing to the devel- 

 opment of tuberculosis the opsonic content of the blood tends to 

 be abnormally low in fully 50 per cent, of the cases. Then, again, 

 we can conceive that the normal bacteriolytic power of the blood 

 may be impaired by some of the influences in question. In the case 

 of chronic alcoholism, this has indeed been demonstrated by Abbot 

 and Bergey, who noted that there was a diminution of complement. 



That this in turn may actually diminish the resistance to certain 

 infections has been shown by Pfeiffer and Moreschi. These investi- 

 gators injected a series of guinea-pigs intraperitoneally with a fatal 

 dose of cholera vibrios (equal for all animals) and an amount of 

 cholera immune serum sufficient to protect the animals against the 

 number of organisms used. At the same time they received varying 

 amounts of normal human serum and a constant quantity of an anti- 

 human rabbit serum. The latter, of course, contained precipitins 

 for the human albumins, and the idea of the experiment was that 

 as a consequence of the interaction between precipitin and precipi- 

 tinogen (albumin), and the resultant formation of a precipitate 

 the complement of the guinea-pig would be absorbed, and accord- 

 ingly not be available to activate the anticholera amboceptors, so 

 that the animal would lose the protective influence of the latter 

 which would have been operative had complement been available. 

 The results were quite in accord with the theoretical demands, 

 all those animals having died in which occasion for complement 

 elimination was afforded, while the control animals which had 

 received no human serum, but which had otherwise been treated 



