242 



STRONG. 



On November 17 a blood examination of all the animals was made. In rats 

 numbered 1 and 4 no parasites whatever were found; in rats numbered 2 and 3 

 very few parasites were seen; in rats numbered 5 and G a moderate number of 

 parasites were encountered. On November IS no parasites were found in rat 

 number 2 but in rat number 3 they had increased in number; in rat number 5 

 they were still present. 



November 21, rat number 7, a normal rat, was injected with African spiro- 

 chaetae and rat number 8, a normal rat, with American spirochajtae. On November 

 23 microscopical examination showed rats numbered 1 to 6 all to be free from 

 parasites; rats numbered 7 and 8 each showed moderate infections with spiro- 

 ckaetae. The animals were all bled to death and the serum separated. 



The following precipitin reactions were performed : 



Conditions 



of reaction. 



Precipitin 

 reaction. 



Serum of— 



Plus serum of — 



Rati (immune to African S) 



Rat 2 (immune to African S) . - 



Rat 3 (immune to African S) 





Negative. 

 Do. 

 Do. 

 Do. 

 Do. 

 Do. 

 Do. 







Rat 8 (infected with American S)i 



Rat S (infected with American S) 



Rat8 (infected with American S) 





Rat 6 (immune to American S) 



Rat 1 (immune to African S) 





The following agglutination reactions were performed: 



Conditions of reaction. 



Agglutination, 



Serum of— 



Plus citrated blood of— 



dilutions 1 to 10 



Rat 1 (immune to African &)__ 

 Rat 1 (immune to African S) . 

 Rat 2 (immune to African S) 

 Rat 5 (immune to American S)_ 

 Rat 5 (immune to American S) 



Rat 6 (immune to American S) .... 



Rat 7 (infected with African S) 



Rat 8 (infected with American S). . 

 Rat 7 (infected with African S) _ _ 



Rat 7 (infected with African S) 



Rat 8 (infected with American S) . 



Rat 8 (infected with American S) 



Strong reaction. 

 Negative. 

 Strong reaction. 

 Negative. . 

 Positive reac- 

 tion. 

 Negative. 



The above-described experiments demonstrate that the precipitin re- 

 action in the manner employed is of no value for the purpose either 

 of the differentiation of the spirochsetas of relapsing fever or for the 

 diagnosis of the infection. It would appear from the series of experiments 

 numbered 3 and 4, that during immunization with these spirochaatse, as 

 in some bacterial infections, the agglutinins and bacteriolysins become 

 developed in demonstrable quantities more quickly than the precip- 

 itins. It is very probable that an animal might be sufficiently highly 

 immunized so that a precipitin test for these spirocluetje could eventually 

 be obtained; but the above experiments conclusively demonstrate that 

 this test is not a practical one as a means of diagnosis of the infection. 



