568 



INFECTION AND IMMUNITY. 



Little or nothing can be done in the way of 

 general proplrylaxis. Washing of the nose and 

 mouth with antiseptics during an epidemic may 

 reasonably be practiced, but with what success is 

 uncertain. The aged and those of low vitality 

 should avoid exposure to infection,, for in them the 

 severer complications, such as pneumonia, are 

 more likely to occur. When influenza conjuncti- 

 vitis appears epidemically in schools, the latter 

 should be closed or the infected children excluded. 

 immunity, Although little or nothing is known concerning 

 bfut^axui ^ e possibility of a natural immunity in man, ex- 

 Recurrences. perience teaches that he is, on the whole, very sus- 

 ceptible. The belief expressed by some that nurs- 

 ing children are less susceptible than older people 

 seems to have some foundation, although it is well 

 known that they are not entirely immune. Influ- 

 enza is sometimes cited as an infection in which 

 one attack creates a predisposition for a second, 

 but the truth of this is doubted by many who have 

 had extensive experience with the disease. Wutz- 

 dorff, in a study of the epidemic which prevailed 

 in Germany during 1891-92, finds in the small 

 number of cases, the irregularity of their distribu- 

 tion, and compartive exemption of rather large 

 districts, reasons for believing that one attack con- 

 fers a degree of acquired immunity ; that is to say, 

 the population had been so thoroughly infected 

 during the preceding year or two that compara- 

 tively few remained who were susceptible, although 

 the disease itself appeared to be more malignant 

 than in the previous year (cited from Beck). 

 However, the occurrence of second attacks shortly 

 after the first, and of repeated infections in some 

 individuals indicate that acquired immunity is of 



