COMMUNICABLE DISEASES 379 



top of the upper layer a turbid ring exhibiting a green fluorescence 

 develops. The reaction is said to be most distinct with urine from 

 persons suffering with paratyphoid A, but also with that of persons 

 suffering with typhoid and paratyphoid B. 



The decade just passed has proved to the entire world that typhoid 

 fever is one of the readily preventable diseases. This is done by means 

 of the bacterins (ordinary and sensitized). As the result of the use of 

 these agents typhoid fever has been driven from the army. The bacterins 

 establish immunization which is an efficient as the vaccination against 

 mallpox. It now lies within the means of everyone to protect himself 

 agaihst this disease. (See also the army statistics mentioned under 

 serobacterins) . 



For some time the human typhoid carriers (that is, persons who har- 

 bored the typhoid organism without showing signs of the disease) have 

 received much attention and numerous cases 

 have been traced to such carriers. The at- ^ o Q 



tempts to free such carriers from the infecting ^ o ^ ^ & ^ 



organisms have as a rule, not met with ^ ^ =^ ^ <=> 



general success. ^X ^^^ 



C. Pneumonia. Pneumonia with its <^^^Q <? ^ 

 modifications, as broncho-pneumonia, capil- ^ ^ Q ^ 



lary bronchitis, pleuro-pneumonia, pneumonic . ^ ^ ^ ^0 ^ 

 pericarditis, etc., is estremely common. The ^ ^ ^ 



primary cause of pneumonia is the Dip- 



FIG. 93. Bacillus pneumonias 

 loCOCCUS pneumomae of which three types O f Friedlander, also known as 



(type I, type II and type III) and one group Bacillus mucosus. This organ- 



. or- j sm ls non _ S porogeneous and is 



(group IV) are recognized. Types I and II easily killed, 

 cause about 33 per cent, of all cases. Type 



II occurs in about 10 to 15 per cent, of cases which are very 

 severe with a morality rate of 50 per cent. The group IV 

 form the causative organisms in about 45 to 50 per cent, of cases, 

 having about the same mortality rate as for groups I and II, namely 

 10 to 15 per cent . The important predisposing causes are exposure to 

 wet and cold, weak lungs, infancy, old age, general debility and alcoholism. 

 It is generally limited to the respiratory tract and the contiguous tissues, 

 as the pericardium and the pleurae. Among infants and young children 

 and those well past middle life, the disease shows a high mortality rate. 

 In youth and early middle life recovery is the rule, provided the physical 

 inheritance and development is good. The mortality rate among those 

 addicted to the use of alcoholic drinks, and those affected with "tobacco 

 heart," is very high. 



One attack of pneumonia is supposed to increase the resisting power 



