238 STRONG. 



Remarks. — Only in one instance is there a suggestion of a reaction, 

 and this is between the American spirochseta and the African immune 

 serum. With the African spiroehseta and the African immune serum 

 there is no evidence of a reaction. However, since the parasites were 

 very scanty in the serum containing African spiroehseta?, it is possible 

 (here was not sufficient precipitinogen present to give rise to a precipitate. 



SEBIES NO. it. 



Experiments with the African, strain. — Rats numbered 1. 2 and 3 having had 

 one inoculation of African spirochsetse twelve clays previously, were inoculated 

 November 8 each with 0.25 cubic centimeter of mouse's blood, containing fairly 

 numerous African spiroehseta 1 , diluted with saline solution. November 11. micro- 

 scopical examination ; no parasites were found in the blood of any of the rats. 

 Evidently relatively immune to the infection. 



Rats numbered 4, 5, 6 and 7 (all normal rats) were each infected on November 

 S with 0.25 cubic centimeter of the same mouse's blood containing African 

 spirochsetse used to immunize rats numbered 1, 2 and 3. November 11 one rat, 

 number 5, has succumbed. In numbers 4 and 6 a few spirochsetse are present in 

 the blood. In number 7 the parasites can not be found. 



November 12 a blood examination of rats numbered 1 and 2 again shows no 

 spirochete to be present. The animals were bled to death, the blood put aside 

 for one and one-half hours and then centrifugated and the serum drawn off. 

 A blood examination of rats numbered 4, 6 and 7 shows in each instance fair 

 numbers of spirochsetse; more were found to be present than in the examination 

 of November 11. Numbers 4 and 6 were also bled to death, the blood centri- 

 fugated, placed aside for a few hours and the serum drawn off. 



Experiments with the American strain. — Mice numbered 8 to 14 have had one 

 previous infection with American spirochetal ten days previously; they were 

 reinoculated November 8, each with 0.125 cubic centimeter of mouse's blood, 

 containing numerous American spirochete, diluted with saline solution. Novem- 

 ber 11 an examination of the blood shows the absence of spirochete in the 

 circulating blood. The animals are evidently immune. 



November 8, rats numbered 15 to 18, normal rats, each infected with 0.25 

 cubic centimeter of mouse's blood containing numerous American spirochete. 

 This same blood was used to immunize mice numbered 8 to 14. 



November 11 all of these rats (numbered 15 to 18) are found to be infected 

 with spirochete, although only a few of the parasites are present in the circulat- 

 ing blood. 



November 12 an examination of mice numbered 8 to 14 shows no spirochete 

 in the circulating blood. Numbers 8 to 12 were bled to death and serum col- 

 lected. Rats numbered 15 to 18 were also examined, only one, number 15, shows 

 a rather rich infection, while the others show very few parasites, although 

 more are present than on November 11. Rat number 15 was bled to death and 

 the serum collected. 



