164 APPLIED BACTERIOLOGY 



Faulty sanitary conditions may assist in the spread of 

 this disease by preparing the throat for the bacillus, and 

 may in this way apparently give rise to cases which would 

 never have arisen had it not been for the existence of 

 such conditions. 



It is also a matter of common experience that an epidemic 

 of true diphtheria is sometimes preceded by a prevalence 

 of ' sore throat,' which seems to gather in intensity till 

 cases arise of which the clinical character shows them to 

 be undoubtedly true diphtheria. No doubt the systematic 

 bacteriological examination which is now being undertaken 

 in several districts will do much to increase our knowledge 

 of these obscure points. 



It has been found that during diphtheria epidemics, 

 dogs, cats and cows may all suffer from a disease which 

 appears to be identical with human diphtheria. 



Pathogenesis. — The incubation period varies from two to 

 seven days, but is usually from about two to four days, 

 while the mortality due to diphtheria is about 0*20 per cent, 

 of the total death-rate. 



In a typical case of diphtheria a white membranous 

 coating is found covering the fauces, tonsils, and uvula, 

 from which it may be spread into the larynx and trachea. 

 Traumatic diphtheria may arise through the organism 

 coming into contact with an abraded surface. 



In diphtheria we have to deal chiefly with a poison 

 elaborated by the growth of the bacillus; and therefore, 

 whether antitoxin or any other form of treatment is to be 

 applied, it is of pressing importance to circumscribe its 

 growth by antiseptic treatment as far as possible. 



An attack of diphtheria affords little or no protection 

 against a second, and, as in many other diseases, the 

 mortality is greatest at the beginning of an epidemic. 



Antitoxin Treatment of Diphtheria. — The theory of arti- 



