THEORIES OF KELAPSES 429 



Relapses 



Various hypotheses have been advanced to account for the 

 relapses which occur in typhoid and undulant fevers. Chante- 

 messe and Widal 1 showed that if the B. typhosus is injected into 

 an animal together with toxins of the streptococcus, B. coli, or 

 Proteus, its virulence is enhanced, or the animal's resistance may 

 be lowered. If, then, immunising and bactericidal properties of 

 the blood and tissues are but slightly acquired during the attack, 

 an absorption of toxic substances from the alimentary tract may 

 be sufficient to give the typhoid bacilli still present a fresh start, 

 and so produce a relapse. This Sanarelli 2 was able to do experi- 

 mentally. This " sensitisation " may be the cause of relapses in 

 rheumatic fever. 



Wright and Lamb 3 suggested that colonies of the organism in 

 the spleen or other organs may be protected from the anti-bac- 

 terial substances which bring the attack to an end by being 

 within a thrombus, or by becoming encapsuled. Then as the anti- 

 bacterial substances diminish in quantity, these colonies resume 

 growth, and a fresh development of organisms ensues with the 

 occurrence of a relapse. 



A third theory was suggested by Durham. 4 He regards a 

 given infection as due to the " result of the action of a sum of a 

 number of infecting agents, each of which is similar but not 

 identical in its nature," the apparently simple infection being 

 ' ; in reality a complex phenomenon brought about by a number 

 of varieties and sub-varieties of the given microbe." He suggests, 

 therefore, that in a typhoid infection a particular race of typhoid 

 bacilli is in excess, and when the an ti -bodies for this particular 

 race have been formed in sufficient quantity, the disease process 

 conies to an end. There may, however, be present at the same 

 time other races which have produced little of their specific anti- 

 bodies ; these then begin to grow and multiply, and a relapse 

 ensues. 



The acquisition of the state of "fastness" by bacteria and 

 protozoa under the influence of specific serums and drugs has 



1 Ann. de VInst. Pasteur, vi, 1892, p. 755. 



2 Ibid, vi, 1892, p. 721 ; and ibid, viii, 1894, p. 193. 



3 Lancet, 1899, vol. ii, p. 1727. 



4 Journ. Path, and Bact., vol. vii, 1901, No. 2, p. 240. 



