CH. VII] VARIATIONS IN PATHOGENICITY 99 



and Gordon (1905). They describe an epidemic in Hertford- 

 shire characterised by an extraordinary diversity of symptoms 

 in different patients. In some cases there were sneezing, 

 coryza, and the ordinary symptoms of a common cold. In 

 other cases patients had "aches and pains all over," stiff neck 

 and suffered subsequently from great debility; such cases 

 had all the appearances of influenza. In others, again, the 

 illness closely simulated scarlet fever ; it began with sore 

 throat, rigors, vomiting, headache, fever and rapid pulse, and 

 was accompanied by a punctate rash at the end of the first 

 24 hours (followed later by desquamation), the " strawberry " 

 tongue, circumoral pallor, enlarged cervical glands which in 

 some cases suppurated, and, in some patients, complications 

 such as nephritis, arthritis and otorrhoea. A fourth type 

 resembled diphtheria and exhibited a suspicious membrane 

 on the tonsil. A fifth type was notified in some cases as typhoid 

 fever and was characterised by epistaxis, melaena, prostra- 

 tion and, in some cases it is stated, a positive Widal reaction. 

 Finally, a number of cases, particularly amongst children, 

 resembled cerebrospinal fever and were so diagnosed ; these 

 were characterised by profuse nasal discharge, pain in the 

 back of the neck, headache, photophobia and irritability, 

 dilatation of one or both pupils, persistent vomiting, drowsi- 

 ness, head retraction, paralysis, coma and, sometimes, con- 

 vulsions and death. 



Sometimes these widely divergent types were exhibited 

 by the different members of a single family or household 

 struck down by the disease, either simultaneously or con- 

 secutively. After a thorough investigation these observers 

 were convinced that the outbreak of these various types of 

 illness was due to the prevalence and spread of only one 

 disease and not a number of different diseases, and a bacterio- 

 logical examination of a large number of cases by Gordon 

 showed that the disease was due to infection by an organism 

 closely resembling, if not identical with, M. cata/rrhcdis. 



4. In the fourth place, the same species of organism may 

 give rise in different epidemics to widely different types of 

 disease. For example, strains of B. influenzae may give rise 



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