THE WAR WITH THE MICROBES. 489 



A relationship was thus established between the poisons from higher 

 plants and from the lowest plants, and certain animals. Was this 

 poisonous property of these bacterial substances due to a true proteid, 

 or was there an admixture of an active, ferment-like substance with 

 the proteid, and are these poisons mechanically carried down in the 

 process of precipitation of the albuminoid matter in the culture liquids'? 

 Experiments show that while the poisons may be proteids, it is 

 more than probable that they are simply carried down with proteid 

 matter as indicated. Brieger in 1893, in view of the results so far 

 obtained, endeavored to isolate the pure poison from cultures of the 

 tetanus bacillus. The cultures were first filtered through porous porce- 

 lain, a Chamberland filter tube, for instance, and the liquid which 

 passed through was treated with a concentrated solution of ammo- 

 nium sulphate. This precipitated the poisons and a number of other 

 substances which gave proteid reactions. After purification and dial- 

 ysis the poison was obtained as yellow, soluble flakes which no longer 

 gave proteid reactions. It was a substance in which there was no 

 noticeable phosphorus nor sulphur. It was thus proved that the 

 tetanus poison belonged neither to the ptomaines before referred to nor 

 to the proteids. The poison, while not perfectly pure, was purer than 

 any ever before obtained, and was so poisonous that a mouse weighing 

 one-half ounce was killed by yj2 s"ooo part of a grain, while -oiu of a 

 grain should kill a man weighing 150 pounds. 



It is not difficult to understand how if the tetanus bacillus outside 

 of the body can produce such powerful poisons, it can give rise in the 

 animal organism to serious troubles. The diphtheria bacillus is another 

 germ which forms very powerful poisons in the solutions upon which 

 it feeds. As already mentioned, some authors, Boux and Yersin, believe 

 that this poison also belongs to the ferments like trypsin and pepsin, 

 while Brieger and Fraenkel thought it was a toxalbumin. We find, 

 after the germ has been removed from the culture liquid by filtration, 

 that the poison can be separated by calcium phosphate or ammonium 

 sulphate, just like the tetanus poison. In the purest condition in which 

 it has been so far obtained it fails to give the proteid reaction, and -^ 

 of a grain will kill a guinea pig. It dialyses readily. Bodies of a sim- 

 ilar kind have been obtained from cholera, glanders, swine plague, 

 tuberculosis, and anthrax cultures, while many other bacteria produce 

 soluble intensely poisonous substances in artificial cultures as well as 

 inside the animal body. 



These juoducts ar(J a n characteristic of the individual organism. 

 The conditions under which the most poisonous ones are formed seem 

 to be dependent partly, we may say, upon the humor of the germ and 

 also upon the food offered for its use. It appears, for example, in con- 

 nection with the diphtheria germ that if there happens to be present in 

 the beef broth upon which it is being cultivated an undue amount of 

 glucose and an insufficient supply of alkali that, instead of producing 



