402 INFECTION AND IMMUNITY. 



Aside from the local influence of the streptococcus, 

 however, a general invasion by this organism may 

 occur, with such consequences as acute nephritis 

 or lobular pneumonia, and in this condition the 

 diphtheritic infection may fall into the back- 

 ground in importance (septic diphtheria). Post- 

 diphtheritic suppurations commonly are caused by 

 the pyogenic cocci, but sometimes in association 

 with the diphtheria bacillus itself. Barely the 

 bacillus is found in pure culture in lobular pneu- 

 monia, a condition which Flexner and Anderson 

 produced experimentally in animals. In puer- 

 peral infections with the streptococcus a puerperal 

 diphtheria is sometimes superimposed. 



immunity and Very young children resist diphtheritic infec- 

 ceptibmty. ^^ ^ certain degree of immunity may be trans- 

 mitted by the mother. Observations on animals 

 show that when the blood and milk of the mother 

 contain antitoxin, the offspring acquires some pro- 

 tection, which, however, may disappear after the 

 cessation of nursing. Polano claims that anti- 

 toxin passes from the mother to the child through 

 the placenta. From the second to the seventh or 

 eighth year children usually are very susceptible. 

 This susceptibility is not uniform, however, for 

 many children escape infection, whereas others, 

 under the same conditions, contract the disease. 

 Following this period susceptibility decreases and 

 after the fifteenth year the disease is relatively 

 rare. 



The cause of the immunity which develops in 

 the absence of a preceding infection has not been 

 sufficiently investigated. In some cases consid- 

 erable amounts of antitoxin are found in the 

 serum, perhaps enough to account for the immun- 



