536 BIOLOGY OF PNEUMOCOCCUS 



jected increasing doses on four successive days, followed by a ten- 

 day rest period. In a comparison of results of different schedules 

 of injections of vaccines in rabbits, Yoshioka (1923) 1562 tried 

 three series of six daily injections at intervals of eight days, but 

 reported better results when the same dose was given in six aliquot 

 parts at one-half hour intervals in one day. Two years later 

 (1925), the same author 1565 reported the results of a more exten- 

 sive study in mice. One group of animals received three doses of 

 vaccine in a period of two weeks; a second was given injections 

 daily for three days; a third was injected six times at one-half- 

 hour intervals in one day ; and the fourth group was given one 

 single injection. The total amount of antigen administered was the 

 same in each group. Yoshioka decided that the best results were 

 obtained by giving the vaccine to animals in divided doses at fre- 

 quent intervals, as in the third group. Killian, 708 however, failed to 

 confirm the observations. 



Barnes and White 86 investigated antibody production in rabbits 

 receiving intravenous injections of formalinized and heat-killed 

 Type I pneumococci under three different schedules: 1) a single 

 injection on each of three successive days ; 2) a single dose on each 

 of five consecutive days; and 3) a series of six injections, one on 

 each of the first two days with the other four at one and one-half- 

 hour intervals on the third day. Of the three plans, the first and 

 last yielded better results than the second, and the first was at 

 least as good as the last. The first scheme corresponds to the so- 

 called "three-week" schedule. In the routine immunization of 

 horses it has been found to give satisfactory results and is, more- 

 over, convenient. According to the three-week schedule of immuni- 

 zation, the following plan has been used at the Massachusetts 

 Antitoxin and Vaccine Laboratory: The horses are injected on 

 Tuesday, Wednesday, and Thursday of one week and on Thurs- 

 day, Friday, and Saturday of the following week. The animals are 

 bled on Monday, the ninth day after the last injection in the 

 course, and the same schedule of injections is resumed on the day 

 following the bleeding. 



