368 A MANUAL OF BACTERIOLOGY 



The vaccine deteriorates on keeping. Emulsions of agar 

 cultures and autolysed cultures have also been used for 

 preparing vaccines. 



Inoculation is now being extensively practised, and 

 Leishman (loc. cit.) gives the following statistics of its 

 value : total number under observation, 18,483-19,314 ; 

 average period under observation, twenty months ; number 

 inoculated, 10,378 ; number uninoculated, 8936 ; case- 

 incidence of enteric per 1000, inoculated 5'39 0*48, 

 uninoculated 30*4 1-23 ; case-mortality per 100, inocu- 

 lated 8'9, uninoculated 16'9. In the French navy Chante- 

 messe states that during nine months in 1912, among 

 67,843 unvaccinated persons 542 cases of typhoid fever 

 occurred, while among 3107 vaccinated ones not a single 

 case of typhoid occurred. 



Variation of the B. typhosus. Allusion has already been 

 made to T wort's work on the " education " of B. typhosus 

 to ferment lactose, and on the apparent conversion of 

 B. typhosus into B. alkaligines by Horrocks (p. 6). Penfold 

 also records variations in the fermentive powers of B. 

 typhosus (Journal of Hygiene, vol. xi, 1911, p. 30). 



Relapses 



Various hypotheses have been advanced to account for the 

 relapses which occur in typhoid and other diseases (e.g. Malta and 

 relapsing fevers). Chantemesse and Widal x 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 experimentally. Wright and Lamb formulated 



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



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



