246 THE DIPHTHERIA BACILLUS 



intoxication. In a few severe cases of diphtheria however the organism has been 

 found after death in the blood and internal organs (Babes, Spronck, and others) : 

 and it is frequently found in the broncho- pneumonic patches which follow an attack 

 of croup (Lceffler, Kutscher). 



The bacillus is also found in the mouths and nasal cavities of persons who have 

 suffered from diphtheria, sometimes for many weeks after recovery from the disease. 

 [" In 3 weeks about 30 per cent, of diphtheria patients are free from morphologically 

 typical diphtheria bacilli. In 20 per cent, the bacilli persist for 4 weeks, in 16 per 

 cent, for 5 weeks, and in 11 per cent, for 7 weeks. One per cent, harbour them 

 for 15 weeks and in exceptional cases they remain in the throat for 30 weeks, though 

 even more prolonged periods of persistence are recorded " (Graham-Smith). Fully 

 virulent diphtheria bacilli have been recovered after as long as 335 days (Prip), 

 230 days (Schafer), 215 days (Belfanti) : these and other observations " conclusively 

 prove that diphtheria bacilli are capable of retaining their virulence during very 

 prolonged persistence in the throats of infected persons " (Graham-Smith). ] l 



[Diphtheria bacilli, a very large proportion of which are virulent, are also present 

 in the throats and noses of " contacts " persons who have recently been in intimate 

 connexion with the disease. It would even appear that less than half the number 

 of individuals in whom the bacillus obtains a lodgment are attacked by the disease. 

 Graham-Smith gives statistics which show that amongst infected families (relatives 

 and attendants) 36*6 per cent, are liable to become infected, while the mean per- 

 centage of infection amongst inmates of hospital wards and institutions is 14 per 

 cent, "and amongst scholars of infected schools 8*7 per cent. ] 



Though the fact is denied by several writers there can be no doubt but that the 

 diphtheria bacillus may occasionally be found in the mouths of persons who 

 have not been in contact with diphtheria : [but an investigation in England showed 

 that of 2132 persons who had not so far as could be determined been exposed to in- 

 fection 0'18 per cent, were found to be harbouring a virulent diphtheria bacillus and 

 2 '62 per cent, non- virulent bacilli, and in the absence of further evidence these 

 figures undoubtedly point to the conclusion "that virulent diphtheria bacilli are 

 seldom if ever present in the throats of healthy persons who have not 

 recently been in contact with cases of diphtheria or infected contacts " (Graham- 

 Smith).] 



2. In the lower animals. 



[Cows. According to Klein cows can be experimentally infected with diphtheria, 

 and lesions containing diphtheria bacilli may appear on the teats and udders as a 

 result of the infection : diphtheria bacilli may also be present in the milk after 

 experimental inoculation. From these observations Klein inferred that cows might 

 naturally suffer from diphtheria and that the milk of such cows might be a cause 

 of human infection. 



[Klein's experimental results have not been confirmed and most observers hold 

 that there is no evidence that diphtheria is a bovine disease (Graham-Smith). 

 On two occasions however virulent diphtheria bacilli have been recovered from spon- 

 taneous lesions of the udder and teats of cows. In one of these cases investigated 

 by Dean and Todd these observers came to the conclusion that though diphtheria 

 bacilli were present, the lesions in the cow were not due to that organism. In the 

 other case Dean and M'Conkey independently isolated the diphtheria bacillus from 

 the lesions in the cow but neither the source of the bacillus nor its relation to the 

 ulcers was determined. 



[Horses. The diphtheria bacillus has only once been isolated from the horse. It 

 was then found by Cobbett in a purulent and slightly sanguineous discharge from 

 the nose of a pony. 



[Cats and fowls and other animals. " Both cats and fowls have frequently been 

 regarded as carriers of the disease, but the bacteriological evidence in support of 

 these statements is unsatisfactory. Instances of natural infection amongst other 

 animals are unknown, though bacilli closely resembling diphtheria bacilli in many 

 of their characters have been found in dogs, guinea-pigs, rats, fowls, turkeys and 

 pigeons " (Graham-Smith). 



[These observations on the occurrence of diphtheria in the lower animals may be 



1 The Bacteriology of Diphtheria, edited by G. H. F. Nuttall and G. S. Graham-Smith ; 

 Camb. Univ. Press. 



