SPUTUM SEPTICEMIA 391 



from such animals is not always of value in either preventing 

 infection in other animals in which it is injected or of miti- 

 gating or curing infections already established in animals. 



It is only by keeping in mind the foregoing facts that we 

 are able to appreciate the difficulties surrounding the problem 

 of pneumonia or to properly estimate the value of certain 

 important experimental results having a bearing upon it. 



Given a group of persons with virulent pneumococci in 

 their mouths, noses and pharynges, why is it that some may 

 develop pneumonia and others remain in health? 



It has been customary to reply: that in those developing 

 the disease there has been a lessening of the general vitality 

 (resistance) through a variety of agencies, to a point that 

 enables the pneumococcus, hitherto present only in a com- 

 mensal relationship, to exhibit its pathogenic activities. 

 This is plausible, but that is all. There is nothing definite 

 in the way of experimental evidence to support it. 



The most satisfying explanation of the beginnings of 

 pneumonia is that offered by the investigations of Meltzer^ 

 and his associates. They demonstrated that if fairly large 

 amounts (5 or 6 c.c.) of fluid cultures of pneumococci be 

 insufflated into the lungs of dogs, that many of the bron- 

 chioles became occluded as the result of the exudation 

 following such insufflations. The occlusion converts the 

 termini of those bronchioles, with their alveoli, into tiny 

 cavities. In such cavities the pneumococci develop and 

 produce irritating substances which in time bring about 

 more or less extensive inflammation of the lung tissues 

 round about them. The characteristics of these inflamma- 



» Jour. Exp. Med., 1912, xv, 133. 



