IMMUNITY 75 



the particular kind of germ introduced and not for 

 others. The bodies producing this increased eating 

 or phagocytosis, opsonins, are supposed not to act 

 upon the white cells, but upon the bacteria and 

 make them more suitable as food for the leuko- 

 cytes. These phenomena have put a valuable method 

 of treatment in the physician's hands. In sub- 

 acute localized disorders particularly, but also in 

 definitely acute and chronic troubles, injections of 

 dead cultures of the bacteria, responsible for the 

 condition, are made beneath the skin. The progress 

 of treatment is followed by a long, elaborate test of 

 permitting the leukocytes of the blood of the patient, 

 and as a control, those of a healthy person, to feed 

 upon the bacteria in question in test-tubes kept at 

 body heat. If the number of germs consumed by the 

 patient's leukocytes rises during the course of the 

 treatment, he is considered as benefiting from the 

 injections. His general constitutional condition is 

 closely watched also. It is now attempted to use for 

 " vaccination" a culture made from the patient's 

 disease, the so-called "autogenous vaccine." 



Principles of Vaccine Treatment. To return for a 

 space to active immunity, it is well to consider here the 

 basis of the present-day bacterin treatment. The 

 ordinary vaccination against smallpox depends upon 

 the fact that human smallpox virus passed through a 

 calf for a number of times loses its power to produce 

 smallpox in man. It does retain power to produce a 

 sore, and this sore contains sufficient of the poison 

 related to smallpox virus to stimulate in the vaccinated 

 person a condition resistant to the virus which would 



