Exps. 45, 46. Same mice as in Exps. 37, 38. 14th Dec. 1910. Intra-peritoncal 
injection of 0'3 c.c. defibrinated relapsing fever blood in 0'5 c.c. saline. 
Next day numerous “lashing” forms were seen in the blood of l)oth. 
The day after the spirochaetes had disappeared. 
Exps. 47, 48. 14th Dec. 1910. Subcutaneous injection of 0‘3 c.c. detibrinated 
relapsing fever blood in ()'5c.c. saline. 
The next two days numerous spirochaetes detected. None seen next day. 
The foregoing experiments show that mice can be reinfected by a 
second inoculation made up to 2.5 days after the first successful 
inoculation. 
Attempts to induce a permanent infection. 
Ex]). 49. 26th Nov. 1910. Guinea-pig, injected intra-peritoneally with OT c.c. 
mouse-blood from Exp. No. 29. Examined on two following days with negative 
results. 
Exps. 50, 51, 50 a., 51a. 26th Nov. 1910. Two mice, intra-peritoneal injection 
of 0'3 c.c. blood containing numerous spirochaetes from mouse No. 29, diluted 
in 0'5 c.c. saline. 
Examined with negative results on the 27th, 29th Nov. and 2nd Dec. 1910. 
To exclude the po.ssibility of these two mice being immune, they were injected 
on the 8th Dec. 1910 with 0‘3 c.c. defibrinated relapsing fever blood in 0'5 c.c. 
saline. 
Spirochaetes were found in the blood of both on two following days. 
Exps. 52, 52 a. 29th Nov. 1910. White rat, intra-peritoneal injection of 
0'5 c.c. of blood of mouse showing spirochaetes. 
Examined the following three days with negative results. 
Also in this case the rat was injected on the 2nd Dec. 1910, with 0'3 c.c. 
defibrinated relapsing fever blood and showed next day the spirochaetes in its blood, 
but not the day after. 
Exps. 53, 53 a. Same rat as in Exp. 11. 29th Nov. 1910. Intra-peritoneal 
injection of 1 c.c. of defibrinated mou.se blood showing sifirochaetes. 
Examined with negative results on the 30th Nov. and 2nd Dec. 1910. The 
injection of 0'3 c.c. relapsing fever blood on the 14th Dec. gave a positive result 
next day. No spirochaetes found the day after that. 
Exps. 54, 55, 54 a, 55 a. 26th Nov. 1910. Two mice, intra-peritoneal injection 
of 0-5 c.c. blood from Exp. No. 29. 
Examined with negative results on the 27th, 29th Nov. and 2nd Dec. 1910. 
8th Dec. 1910. Both were injected with 0'3 c.c. defibrinated relapsing fever 
blood and showed spirochaetes in the blood the next and following days. 
Exps. 56, 57. 16th Dec. 1910. Two mice injected intra-peritoneally with blood 
from mou.se in Exp. No. 44. 
One .showed a few spirochaetes next day. It was killed and its blood injected 
into another mouse, with negative results. The other mouse did not show any 
spirochaetes at all, it was examined on three days. 
Parasitology v 
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