306 BACTERIA. 



that has been allowed to grow for forty-two days, proves 

 fatal to a guinea-pig in about thirty hours. Larger doses, 

 from 4 to 20 cc. injected into dogs of various sizes kills 

 them in from fourteen to twenty-six hours. In doses of 

 2 cc. it proves fatal in four to six days. In all cases the 

 symptoms are those of more or less acute poisoning, re- 

 sembling septic poisoning in some respects and phosphorus 

 or metallic poisoning in others. A dose of less than i cc. 

 of the filtered liquid injected into a dog of middle size causes 

 a temporary paralysis, very similar to the post-diphtheritic 

 paralysis of the human subject. It is a curious feature that 

 when paralysis occurs in a rabbit, death invariably ensues ; 

 but in both the pigeon and the dog, especially in the latter, 

 recovery may frequently follow this condition just as in the 

 case of the human being. Sheep are susceptible to the 

 action of diphtheritic poison, but rats and mice are unaffected 

 by it. The effects on other animals have been already 

 mentioned. 



It is always a difficult matter to determine what is the 

 nature of an organic poison. In the first place it is produced 

 in such small quantities that it is difficult to obtain 

 sufficient to determine, even by chemical analysis, its exact 

 nature. Further, it is so unstable that it may become 

 completely altered by the various reagents that have 

 to be used in separating it out from the mixture in 

 which it occurs. A rise of temperature beyond a certain 

 point is fatal to its activity, and it undergoes various oxida- 

 tions under the least provocation. Roux and Yersin consider 

 that this special poison has certain features in which it 

 resembles the diastases. Thus, when heated in sealed 

 tubes over a water bath to 58 C. for a couple of hours, 

 the toxic activity is diminished at least seven-eighths of its 

 original power ; whilst very large doses of the filtered poison 

 that has been heated to 100 C. may be introduced into the 

 veins of a rabbit, or under the skin, without producing any 

 immediate effect, although symptoms are produced later 

 which can only be due to the action of this material as a 

 modified diphtheritic poison. Like diastase, the diphtheritic 

 poison is rapidly modified by sunlight in presence of air, but 

 if air be excluded the diminution in toxic activity brought 

 about by exposure to sunlight is comparatively slight. 



On evaporating a filtered diphtheritic bacillus culture in 



