472 PATHOGENIC MICROORGANISMS 



that the treatment should be vigorously continued by remjections 

 every 8 or 10 hours, as often as it seems advisable. 



Serum disease which occasionally follows is similar to that which 

 follows diphtheria antitoxin injections. 



In discussing the results of serum treatment no final judgment 

 can be given. There have been all kinds of extravagant claims both 

 as to usefulness and uselessness of the serum. Cole's judgment we 

 consider to be entirely objective and unprejudiced in this matter, and 

 he states from his own experience that he has obtained no results with 

 any serum except type I. With this serum, however, he believes that 

 there has been a definite drop in the mortality, to about 8 per cent 

 as contrasted with a normal mortality of 20 per cent, or more, in 

 untreated type I cases. In general, this opinion seems to have been 

 borne out by other observers who have used the method. It is of the 

 greatest importance that in judging of results of such treatment a 

 discrimination should be made between cases that have been treated 

 promptly in the early stages of the disease, and those in which the 

 treatment has been delayed, for, as every bacteriologist knows, when 

 dealing with the pathogenic Gram-positive cocci, that no amount of 

 serum will save an experimental animal when once an extensive 

 septicemia has been established. 



EPIDEMIOLOGY OF PNEUMONIA 



Pneumonia is endemic in most well-populated centers of the world, 

 but seems to be particularly frequent in the temperate zones. The 

 disease is present sporadically at almost all times of the year, but is 

 particularly frequent during the colder months, usually reaching its 

 annual peak in this latitude during February or March. It is not 

 commonly an epidemic disease, but may become so under conditions of 

 crowding, and wholesale exposure to wet and cold, incident to military 

 life, or the life in mining camps, etc. Wherever, in other words, very 

 close association of limited groups of people takes place under condi- 

 tions of poor hygiene and crowding with coincident hardships of 

 various kinds, pneumonia epidemics are apt to occur. The most exten- 

 sive epidemics which have occurred within the last 20 years are those 

 which took place in the South African mining districts, in Panama, 

 and during the World War in the camps and among the armies at the 

 front. Pneumonia of all kinds in ordinary times accounts for about 



