April 24, 1908] 



SCIENCE 



649 



mortality following upon the injection of 

 a uniform dose of 0.25 c.e. of spirillar 

 blood, the infection with 8. Obermeieri 

 is mildest with barest indication of re- 

 lapses and that with S. Duttoni is most 

 severe; death usually results, or re- 

 lapses occur regularly and are repeated, 

 time and again. In general, the four spi- 

 rilla can be readily separated into two 

 groups, the Moscow and New York strains 

 falling together, while the two African 

 strains are more closely allied than with 

 either of the others. In the African strains 

 a notable feature is the peculiar massing 

 of red-blood cells, which feature enables 

 one by mere microscopic examination of 

 the fresh blood to decide which of the two 

 groups is concerned. There are also dif- 

 ferences in size, the African group showing 

 spirilla which are fully twice as long as 

 those of the first group. A full discussion 

 of the differences will be taken up else- 

 where. 



The study of the immunity or serum 

 reactions of these four strains of spirilla 

 presents interesting facts regarding their 

 relationship and incidentally brings up the 

 question of the value of the so-called spe- 

 cific reactions as a reliable means for the 

 differentiating of species. The question as 

 to what constitutes a species, itself a dif- 

 ficult one in connection with the higher 

 forms of life, becomes far more difficult 

 to answer when it concerns the uni- 

 cellular organism which seemingly is 

 incapable of presenting any fixed char- 

 acteristic. Variation in the ordinary 

 morphological and biological properties 

 is the rule among protists and the serum 

 reactions which are looked upon as 

 the most specific characteristics seem to 

 offer no exception. The differences in 

 these reactions must be considered as an 

 expression of changes in the molecular 

 composition of the living protoplasm, and 

 for each set of new conditions a new equi- 



librium in the arrangement of atoms must 

 be established. The known examples of 

 tautomerism among the relatively simple 

 organic compounds may serve to illustrate 

 the conception as applied to living matter. 

 In a previous paper we clearly demon- 

 strated the preventive and curative action 

 of the serum of animals immunized to the 

 New York spirillum, and it was, therefore, 

 desirable to ascertain whether similar re- 

 sults could be obtained, under like condi- 

 tions, with the other three strains. With- 

 out going into unnecessary detail at the 

 present time, it may be said that the serum 

 of an immunized rat exerts a prompt cura- 

 tive action in rats infected with the corre- 

 sponding or homologous spirochete, and 

 that in like dosage it is without effect upon 

 the remaining three organisms. This fact 

 can best be seen from the following table : 



TABLE I 



Curative Experiments mith Immune Sera 



It will be seen from the above that of 

 four rats infected with S. Obermeieri, and 

 containing at the time large numbers of 

 spirilla in the blood, the one which received 

 the serum from a rat hyperimmunized to 

 that organism was promptly cured, whereas 

 the sera of the other hyperimmune animals 

 were without any apparent effect. A like 

 specific curative action is obtained with the 

 other organisms when the homologous 

 serum is used. By a "cure" is meant the 

 total disappearance of the spirilla from the 

 peripheral blood in from one half to four 

 or six hours. This curative effect may be 

 permanent or it may be followed by a slight 

 relapse in the course of seven or ten days. 



