700 



SCIENCE 



[N. S. Vol. XXXVI. No. 934 



quires the assistance of the immunity 

 principles. Acting together the two agents 

 quickly bring the infection under control 

 and recovery follows. This happens even 

 after the pneumococci have entered the 

 blood stream and begun to multiply there. 

 The effects of the soap and serum com- 

 pound are, however, restricted to the type 

 of pneumococeus represented by the im- 

 mune serum in the mixture.'^'^ When the 

 type of microorganism and serum differ ab- 

 solutely no therapeutic action follows. 

 This obstacle to the practical employment 

 of this method of specific treatment will 

 doubtless be reduced or even wholly set 

 aside by preparing a true polyvalent im- 

 mune serum that will represent not many 

 cultures of the pneumococeus taken at 

 random, but the several types or races oc- 

 curring in nature. We already know the 

 number to be few. 



It has become the custom to speak of 

 these types of microbes as resistant or 

 "fast"; but the term is relative merely. 

 The fact and degree of fastness will be re- 

 vealed by the source of the test-serum. 

 But within a given microbic species this 

 quality of resistance may well appear 

 against chemical bodies as well. Pneu- 

 mococci, for example, vary in properties by 

 gradual gradations in the direction of the 

 streptococcus, which besides differing in 

 still other biological properties chances not 

 to dissolve in bile. The gradients of pneu- 

 mococci approaching the streptococcus are 

 progressively less acted upon by sodium 

 oleate. The trypanosome of sleeping-sick- 

 ness is less subject to the therapeutic ac- 

 tion of certain organic arsenic compounds 

 in some regions in Africa than in others. 

 The antimeningitis serum suppresses the 

 growth and multiplication of most menin- 

 gococci, but not of all. This quality of 



" Lamar, Journal of Experimental Medicine, 

 1911, XIII., 1; 1912, XVI., 581. 



fastness is not alone innate but can be de- 

 veloped artificially as a mutation, both 

 against serum principles and chemical 

 drugs and may persist. Infectious dis- 

 eases showing a strong tendency to relapse 

 in course of recovery are caused by mi- 

 crobes tending to flourish as races or 

 types. Relapsing fevers that pass three or 

 four exacerbations on the way to recovery 

 are attributed to spirochetse assuming a 

 corresponding number of distinct forms. 

 Infections tending to many relapses, of 

 which lues is an example, are attributed to 

 parasites capable of flourishing in many 

 such types of which one part is innate and 

 the other the result of mutations under the 

 influence of curative serum or drug. For- 

 tunately, there appears to be no parasite 

 capable of performing indefinite mutations ; 

 and experience is teaching that the more 

 precise, specific and vigorous the means 

 employed to control infection, the smaller 

 the risk of mutation and the greater the 

 probability of suppression of the parasitic 

 agent of disease. 



In 1886 Theobald Smith^^ first clearly 

 pointed out that the injection of dead bac- 

 teria conferred active immunity to subse- 

 quent inoculation with virulent materials. 

 Now the employment of dead bacteria is 

 widespread both for preventing and for 

 healing disease. Wright^'' especially is to 

 be credited with the general application of 

 the method to therapeutics. While the 

 limits of value of inoculation, as it is 

 termed, are not yet defined and it promises, 

 theoretically, more for the subacute and 

 chronic than for the acute infections, I am 

 inclined to the belief that to be really ef- 

 fective attention will need more and more 



'" Salmon and Smith, Proceedings of the Biolog- 

 ical Society of Washingtm, 1884-86, III., 29. 



» Wright, Proceedings of the Royal Society of 

 Medicine, 1909-10, III., Supplement, 1. 



