658 PATHOGENIC MICROORGANISMS 



them with liquid air and extracting in 1 : 1000 potassium hydrate. 

 Besredka obtained toxic substances by emulsifying agar cultures of 

 bacilli in salt solution, sterilizing them by heating to 60 C. for about 

 one hour, and drying in vacuo. The dried bacillary mass was then 

 ground in a mortar and washed in sterile salt solution which was again 

 heated to 60 C. for two hours. The remnants of the bacterial bodies 

 settle out and the slightly turbid supernatant fluid contains the toxic 

 substances. 



Vaughan 55 has obtained poisons from typhoid bacilli by extracting 

 at 78 C. with a 2-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 protein substances, 

 believing 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 1 per cent. The 

 cultures are allowed to grow for two or three weeks and then sterilized 

 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 cultures 

 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 

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

 We have ourselves often boiled typhoid suspensions without destroying 

 their toxicity for guinea pigs. 



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 sub- 

 cutaneous 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. 



In unpublished experiments we have perfused the isolated guinea 

 pig heart with typhoid extracts for prolonged periods without killing it, 



