254 MODERN BIOLOGIC THERAPEUSIS 



control the condition in subacute and chronic 

 cases; and it is best, therefore, to use a com- 

 bined vaccine. (3) Again, pneumonia is caused 

 chiefly by the pneumococcus ; but when pneu- 

 monia follows some suppurative condition, the 

 streptococcus and staphylococcus are associ- 

 ated with the pneumococcus. Hence, a com- 

 bined vaccine is indicated. (4) In diseases of 

 the respiratory tract, the micrococcus catarrha- 

 lis or the Friedlander bacillus causes the pri- 

 mary infection; but after secretion has con- 

 tinued a few days the pneumococcus, strepto- 

 coccus and staphylococcus are invariably found. 

 Hence, a combined vaccine is indicated for both 

 the acute and the chronic conditions. 



It is always desirable, however, that a bac- 

 teriologic examination be made to determine the 

 causative microorganism before using a vac- 

 cine, in order that the action of the vaccine may 

 be specific; but it is not always practicable for 

 such an examination to be made and, in most 

 cases, a correct diagnosis may be made from 

 the clinical symptoms. 



WHEN TO USE VACCINES AND WHEN SERA 



When the vitality of the patient is low that 



