Apbeq 24, 1908] 



SCIENCE 



651 



the need of an exact diagnosis as to kind 

 of spirillum present. The lose of a poly- 

 valent serum, obtained from animals im- 

 munized to all four strains (and more), as 

 can readily be done, will perhaps be de- 

 sirable, especially in localities where sev- 

 eral strains are known to occur. At pres- 

 ent the one obstacle in the way of a realiza- 

 tion of a perfect means for the prevention 

 and cure of the various forms of relapsing 

 fever is the failure to obtain artificial cul- 

 tures of the spirochetes. 



While the curative experiments indicate 

 a marked specific action of each serum, this 

 specificity disappears to a certain extent 

 when the serum is used for preventive pur- 

 poses. It will then be found that a given 

 serum may prevent or modify the infection 

 by two or more strains and this fact must 

 be interpreted as indicating a close rela- 

 tionship of such strains. This conclusion 

 is further borne out by cross-immunization 

 experiments with recovered or hyperim- 

 mune animals. Certain it is that the dif- 

 ferences between any two spirochetes, as, 

 for example, Moscow and New York, is no 

 greater than between S. Duttoni and its 

 serum-fast strain. 



TABUB II 



Prevention, Experiments with Immune Sera 



From the above table it will be seen that 

 while a given serum has a perfect pre- 

 ventive action with respect to its own 

 strain, a more or less like action is exhib- 

 ited with reference to the nearest strain. 

 The -\- sigii shows full protection, whereas 

 the ± indicates considerable action as re- 



vealed by delayed or mild infection. "With 

 a larger amount of serum an even more 

 marked overlapping of immunity can be 

 expected, and this is what actually is ob- 

 served when cross-infection is attempted 

 into recovered or hyperimmunized rats. 

 The large amount of immune blood in these 

 animals ensures a greater preventive action, 

 as will be seen by comparing Tables II. 

 and III. 



TABLE in 



Prevention in Hyperimmunized Rats 



The details of all these and other experi- 

 ments must of necessity be omitted at the 

 present time. The facts given, however, 

 clearly show that in relapsing fever we are 

 dealing with a group of related organisms 

 which, while in one sense they can be re- 

 garded as distinct species, after all must 

 be considered as derived from one stem. 

 Further comparative studies must show 

 whether or not this variation is even more 

 common than is indicated by the known 

 four strains. As to the determining factors 

 which bring about these modifications noth- 

 ing definite can as yet be stated, though 

 the conditions involving the preservation 

 of the virus, as pointed out by Marchoux 

 for the chicken spirochete, may be of prime 

 importance. 



Immunity in Bocky Mountain Spotted 

 Fever: H. T. Kicketts and L. Gomez. 

 An attack of Rocky Mountain spotted 

 fever, produced experimentally in the 

 monkey or guinea-pig, is followed by strong 

 and prolonged immunity to second inocula- 

 tions. The ofi'spring of an immune female 

 guinea-pig are immune and their immunity 



