ZOOLOGY, ENTOMOLOGY, AND MEDICINE 245 



A short time after an inoculation is made, the opsonic index 

 falls lower than it was previous to the injection of the vaccine. 

 This was named by Wright the negative phase. Shortly after, 

 from a few hours to several days, the opsonic index will rise 

 above the starting point. This is called a positive phase. The 

 amount of opsonins in the blood remains stationary for a var- 

 iable length of time, and then diminishes. As soon as this 

 diminution is noticed, a second injection of the vaccine should 

 be administered. This second negative phase produced will be 

 less marked than the first, and soon the positive phase comes 

 on, reaching a higher level than that previously. Thus, the 

 injections are repeated from time to time, according to the 

 opsonic index of the patient's blood, and the positive phase 

 attains a higher and higher level until it may be as high or 

 considerably higher than that of a normal person. In other 

 words, if vaccinations are properly given (never during a nega- 

 tive phase,) and as a result the patient's tissues are stimulated 

 in the increased production of opsonins, phagocytosis is in- 

 creased, and the patient rapidly recovers from his infection 

 because the invading bacteria are disposed of. This is the 

 principle mainly to be remembered for successful application 

 of bacterines or vaccines in infectious diseases caused by 

 pathogenic bacteria. 



There are today a great many bacterines manufactured for 

 medical use. Chief among them are the anti-rabic vaccine, the 

 typhoid, pertussis vaccine, meningococcus vaccine, gonococ- 

 cus vaccine, acne vaccines, anti-streptococcic vaccine, pneu- 

 mococcus vaccine, staphylococcic vaccine, and a class of im- 

 portant vaccines which come under the head of tuberculins. 



Wright carried out very extensive experiments in South 

 America with the pneumonia vaccine. He worked under great 

 difficulties and had great trouble in regulating the sizes and 

 frequency of doses. His main guide in the choice of doses and 

 intervals of administration was the ups and downs of the 

 temperature chart, and clinical symptoms. Of one hundred fifty 

 nine cases given the vaccine treatment fifty died, and of one 

 hundred and forty given the expectant treatment, forty-eight 

 died. In his succeeding experiments, larger doses of vaccine 

 were administered and the percentage of death decreased. 



