148 PNEUMONIA 



does not cause pneumonia and that the disease results only when one 

 harbors a more virulent strain. Those who hold to this theory insist 

 that disinfection of all pneumonia sputum and the isolation of those 

 suffering from this disease should be rigidly enforced. Opponents of 

 this theory point out that such measures do not lead to a decrease in 

 the prevalence of this disease. They say that while isolation and dis- 

 infection are followed by a decrease in other infectious diseases, they 

 have had no such effect on pneumonia. A third possibility is that 

 the pneumococcus so constantly the guest of man, becomes virulent 

 when for any reason the vitality of the individual is lowered. To-day 

 this is the prevalent belief and it must be added that it has much sup- 

 port. The frequency with which pneumonia develops after exposure 

 to cold is generally admitted. That form of pneumonia which follows 

 injury to the lung tissue, known as traumatic pneumonia, and the fre- 

 quency and the great fatality of this disease among chronic alcoholics 

 and in the general enfeeblement of old age are illustrations. The safest 

 plan is to isolate the pneumonia patient, to disinfect his expectoration, 

 and to avoid all conditions which render the body more susceptible to 

 this and other bacteria, which may cause this disease. However, it 

 must be added that the epidemic character frequently exhibited by 

 pneumonia leaves no doubt in my mind that exposure to an unusually 

 virulent strain of the pneumococcus is an important factor in the 

 distribution of this disease. 



