160 MICROBES AND TOXINS 



botulismus toxin is fatal in the dose of Yjnj-^ c - c - (by sub- 

 cutaneous inoculation in each of these cases). Toxins are 

 soluble in water and in glycerine, and can be precipitated from 

 solution in virtue of the fact that they adhere to precipitates 

 and coagula ; precipitation is a method of purification. They 

 are unstable or "labile" substances, heat, light, and oxygen 

 destroying them fairly quickly. Exposed for an hour and 

 a half to the temperature of 55 C, the tetanus toxin loses its 

 toxic properties ; at 60 C. it is destroyed in thirty minutes ; 

 at 68 C., in five minutes. Toxins bound up with dried 

 precipitates are more resistant ; the dry tetanus toxin is still 

 slightly active after an hour at 80 C., and even after fifteen 

 minutes at 120 C. Sunlight " inactivates'' a solution of tetanus 

 toxin in fifteen to eighteen hours. When a photo-dynamic 

 substance (e.g., i per cent, eosin), is added, the toxin is 

 " inactivated " after six hours' exposure to light; with 2*5 to 

 5 per cent, eosin it is " inactivated " even in the dark. 



Comparison between Toxins and Diastases. The 

 chemical constitution of diastases is not much better known 

 than that of the toxins. In comparing toxins with soluble 

 ferments or diastases, although it is possible to note analogies, it 

 is for obvious reasons impossible to give a chemical definition. 

 Like diastases, toxins act in a very small dose, are soluble in 

 water and in glycerine, and are weakened by filtration, and are 

 sensitive to the action of oxygen, of heat, and of light ; also 

 to changes in their reactions and to various chemical substances 

 which " poison " or destroy them. Roux and Yersin, who 

 pointed out these analogies at the time of their work on toxins 

 in 1889, did not see in them more than a suggestion: "It 

 seems to us that the diphtheria poison has many analogies 

 with the diastases. Its activity is quite comparable to these 

 and to the activity of venoms. We do not mean, how- 

 ever, that it produces phenomena of hydrolysis such as the 

 diastases produce. It neither inverts sugar nor digests 



gram is organic matter. Supposing that the whole of this is toxin (which 

 is a great exaggeration), the lethal dose for a mouse would be o '000,000, 25 

 gram. 



