330 CLINICAL BACTERIOLOGY. 



favor of the view that the disease is a toxic infection, and 

 that the exciting agent is not itself disseminated into the 

 viscera. The relations between scarlet fever and diphtheria 

 are well known. Scarlet fever is sometimes complicated 

 by true diphtheria with diphtheria-bacilli in the membranes. 

 More frequently, however, scarlatinal angina is due to 

 streptococci. Altogether scarlet fever exhibits a tendency 

 to be complicated by streptococci, and the secondary sup- 

 purative processes that not rarely occur are attributable to 

 these microorganisms. 



The susceptibility of human beings to scarlet fever is 

 greatest between the third and eighth years, though not so 

 great as that of measles. After the tenth year the disease 

 is less common, and still less so in the first year of life. 



Like measles, scarlet fever is more common in winter 

 than in summer. Certain local influences in the distribu- 

 tion of scarlet fever can not be ignored. Although the dis- 

 ease is, on the whole, everywhere endemic in uniform dis- 

 tribution, noteworthy variations occur. Thus, some cities 

 have remained free from scarlet fever for thirty, and even 

 for fifty, years, although in constant communication with 

 other infected cities. 



The immunity after recovery from scarlet fever is active 

 and enduring. Only twenty-nine cases in all of second 

 attacks and four of third attacks are recorded in the litera- 

 ture. 



The large number of bacteria found in cases of scarlet 

 fever, both micrococci and bacilli, require no particular 

 mention. Streptococci have been found most frequently, 

 and these, as in the case of diphtheria, appear to constitute 

 a frequent, perhaps a regular, complication of the virus of 

 scarlet fever. 



WHOOPING-COUGH (PERTUSSIS). 



In its infectivity whooping-cough stands close to mea- 

 sles. Our knowledge of the virus of the former disease 

 is yet quite scanty. The contagium is contained in the 

 breath and, especially, in the expectoration of children suf- 

 fering from whooping-cough. With the sputum it finds 

 its way upon the linen, and it may also be conveyed 

 through healthy persons. Probably infection takes place 

 always through the respiratory tract. Children between 



