BACILLUS OF TYPHOID FEVER 417 



bodies settle out and the slightly turbid supernatant fluid contains the 

 toxic substances. 



Vaughan ' has obtained poisons from typhoid bacilli by extracting 

 at 78° C. with a two-per-cent solution of sodium hydrate in absolute 

 alcohol. In this way he claims to separate by hydrolysis a poisonous 

 and a non-poisonous fraction. He claims, moreover, that this poison- 

 ous fraction is similar to the poisons obtained in the same way from 

 Bacillus coli and the tubercle bacillus, and other proteid substances, 

 beheving that the specific nature of such proteids depends upon the 

 non-toxic fraction. 



A simple method of obtaining toxins from typhoid bacilli is carried 

 out by cultivating the microorganisms in meat-infusion broth, rendered 

 alkaline with sodium hydrate to the extent of about one per cent. 

 The cultures are allowed to grow for two or three weeks and then steril- 

 ized by heating to 60° C. for one hour, and allowed to stand for three 

 or four weeks at room temperature. At the end of this time the cul- 

 tures may be filtered through a Berkefeld or Pasteur-Chamberland filter 

 and will be found to contain strong toxic substances. 



The accounts concerning the thermostability of the various toxins 

 obtained are considerably at variance. In general, corresponding with 

 other endotoxins, observers agree in considering them moderately re- 

 sistant to heat, rarely being destroyed at temperatures below 70° C. 



Intravenous inoculation of rabbits with typhoid endotoxins, if in 

 sufficient quantity, produces, usually within a few hours, a very marked 

 drop in temperature, diarrhea, respiratory embarrassment, and death. 

 If given in smaller doses or by other methods of inoculation — 

 subcutaneous or intraperitoneal — rabbits are rendered extremely ill, 

 with a primary drop in temperature, but may live for a week or ten days, 

 and die with marked progressive emaciation, or may survive. Guinea- 

 pigs and mice are susceptible to the endotoxins, though somewhat 

 less so than rabbits. 



Immunity in Typhoid Fever. — As a rule, one attack of typhoid fever 

 protects against subsequent ones. Although exceptions to this rule 

 may occur, they are so rare that the history of a previous attack of this 

 disease practically excludes its consideration in the diagnosis of any 

 obscure condition. 



Animals may be actively immunized by the injection of typhoid 

 bacilli in gradually increasing doses. In actual practice, this is best 



• Vaughan, Am. Jour, of Med. Sci., 136, No. 3, 1908. 



