208 INFECTION AND IMMUNITY 



disease. In the Bulletin of the Health Department 

 of that city for the month of May, 1903, the follow- 

 ing statement is made : 



"Since the first of January there have been 2891 deaths from 

 pneumonia, as compared with 1321 from consumption and 1238 

 from all other communicable, contagious, or infectious diseases, 

 including diphtheria, erysipelas, influenza, measles, puerperal 

 fever, scarlet fever, smallpox, typhoid fever, and whooping-cough. 

 This is an excess of 382 pneumonia deaths over the deaths from 

 all the other preventable diseases 1570, or 118.8 per cent, more 

 than the deaths from consumption, and 1653, or 133.5 P er cent - 

 more than those from the other specified diseases." 



The micrococcus of pneumonia, unlike the tubercle 

 bacillus, is able to live in the mouths of healthy per- 

 sons, where it finds the necessary pabulum for its mul- 

 tiplication in the normal salivary secretions. While 

 pneumonia may prevail as an epidemic, as a result of 

 the transmission of the disease from the sick to those 

 associated with them, it is well known that many soli- 

 tary cases occur, in families, which cannot be traced 

 to preceding cases and in which the disease does not 

 spread, although no precautions have been taken in 

 the way of isolating the patient or disinfecting his 

 sputa. The infection in such cases probably results 

 from the presence of the micrococcus in the salivary 

 secretions of an individual whose lungs, as a result of 

 " catching cold " or of an attack of measles or of 

 influenza, have become vulnerable, that is, are sus- 



