400 INFECTION AND IMMUNITY. 



were found twenty- two months after recovery. 3. 

 From the upper air passages of healthy persons 

 who may never have had diphtheria, but who have 

 been in direct or indirect contact with the dis- 

 eased. Kober obtained virulent bacilli from 8 per 

 cent, of the individuals who had been in direct 

 contact with patients, and he states that 0.83 per 

 cent, of the people at large carry with them viru- 

 lent organisms. This condition may well account 

 for the "spontaneous" origin of diphtheria in the 

 susceptible. 4. From cases of latent diphtheria as 

 represented by chronic pharyngeal diphtheria and 

 chronic rhinitis fibrinosa. 



Hence, infection takes place chiefly by direct 

 contact, but frequently also by indirect contact. 

 Transmission by kissing or by other means of inti- 

 mate contact, by using infected cups or toys, is 

 well recognized. "Droplet infection," i. e., from 

 infected globules of mucus or saliva which the pa- 

 tient emits when speaking or coughing, may occur, 

 but perhaps is not of great significance. The same 

 probably is true of "dust infection," although, as 

 stated, the organism may remain living and viru- 

 lent in a dried state for a long time. The disease 

 is rarely transmitted from animals to man, al- 

 though such transmission may occur from the cat, 

 which occasionally suffers from true diphtheria. 

 The diphtheria of fowls is due to another organ- 

 ism. 



The upper air passages, more rarely the conjunc- 

 tiva, wounds and the vulva, are recognized as in- 

 fection atria. 



r^^ Q ^ OC8 ^ an( j g enera j phenomena of diphtheria 

 are caused by the soluble toxin which the organ- 

 ism secretes. Although the toxin is not absorbed 



