294 BACTERIA AND DISEASE 



found in the throat of 8 per cent, of these. The second series com- 

 prised 600 individuals who had not recently come into contact with 

 any diphtheria cases from 5 of these a bacillus similar to diphtheria 

 was isolated. It was rather short, with swollen ends, and was not 

 pathogenic to guinea-pigs. Denny of Brooklyn examined 235 

 healthy persons, and found the diphtheria bacillus in one case. Biggs 

 met with 32 cases out of 330 healthy persons, and the Committee of 

 the Massachusetts Board of Health reported that 1-2 per cent, of 

 healthy persons amongst the general public are infected with diph- 

 theria bacilli. Only 17 per cent, of such bacilli appear, however, 

 to be virulent. Goadby examined 100 healthy school children, and 

 found 18 with diphtheria bacilli, but the disease was prevalent in 

 the neighbourhood.* 



It is certain that, as a rule, " healthy " throats do not yield the 

 true B. diphtheria unless those examined have been in contact with 

 infected persons. But that raises the real difficulty in practical 

 public health work. The definitely diseased and the definitely 

 healthy persons can be arranged for. It is the apparently healthy 

 person, who coming into contact with the infected person acts as a 

 " carrier " of infection, that creates the problem. The actual per- 

 centage of such persons varies widely. In infected families it may 

 be 50 per cent. (Park and Beebe), or 100 per cent. (Goadby). In 

 schools and institutions the percentage is, of course, lower. Goadby 

 found it to be 34 per cent, in the Poplar Union Schools, but it may be 

 as low as 7 (Thomas). Aaser found that 19 per cent, of the " contacts " 

 in a soldiers' barracks contained the bacillus in their throats, and 

 Denny found in a truant school that the percentage was 11. In 

 hospital wards it is commonly above 20, and among the general 

 public above 10 per cent.f These figures at once explain the spread 

 of diphtheria. They also suggest the methods of prevention. 



In the ordinary diphtheria epidemic, whether large or small, these 

 methods are mainly five. First, the actual cases of diphtheria must 

 be effectually and promptly isolated. Secondly, the throats of contact 

 persons should be bacteriologically examined, and those persons in 

 whose throats the bacillus is found " carriers " should be isolated, 

 and their throats treated. Thirdly, sore throats in the immediate 

 vicinity of the diphtheria infection should be similarly examined. 

 Fourthly, thorough disinfection should take place in respect of in- 

 fected houses, and inquiry made as to school influences, social habits, 

 etc., of infected households. Fifthly, antitoxin should be used as 

 prophylactic in infected families. 



The new facts respecting the persistence of the bacillus in the 



* See Jour, of Hygiene, 1903 (Graham-Smith), p. 216 ; and 1904, p. 255. 

 t See Jour, of Hygiene, 1904, pp. 258-328 (Graham-Smith) ; and Practitioner, 

 1903, vol. ii., pp. 715-21 (Newman). 



