VACCINES IN PROPHYLAXIS OF DISEASE 173 



salt solution of killed pathogenic bacteria that 

 is, bacteria which are capable of producing dis- 

 ease. Pollen vaccine is an extract of the pollen 

 of various flowering plants, grasses and weeds. 



The therapeutic action of vaccines consists in 

 the stimulation of the tissue-cells of a patient. 

 This stimulation arouses the tissue-cells to the 

 production of various antibodies, as a result of 

 which the patient is protected against the dis- 

 ease. This type of immunity is termed "ac- 

 tive" and may last for a number of years. 



The present widespread use of bacterial vac- 

 cines dates from the demonstration by Wright 

 and Douglas of the presence of opsonins in 

 sera, and the relation of opsonins to phagocyto- 

 sis in health and disease as influenced by the 

 administration of bacterial vaccines. By de- 

 termining the opsonin content of a serum, they 

 were able in many cases to establish the correct 

 dosage of the vaccine and the frequency of its 

 administration. 



PROPHYLACTIC VACCINATION 



The efficacy of inoculation by vaccines, in the 

 prophylactic immunization against certain dis- 

 eases, may be accepted as established clinically 



