i;6 RELATIONS OF BACTERIA TO DISEASE. 



minimal lethal dose of a toxin these factors must be carefully 

 considered. 



The following is the best method of obtaining concentrated extracellular 

 toxins. The toxic fluid is placed in a shallow dish, and ammonium sulphate 

 crystals are well stirred in till no more dissolve. Fresh crystals to form a 

 bulk nearly equal to that of the whole fluid are added, and the dish set in an 

 incubator at 37 C. over night. Next day a brown scum of precipitate will be 

 found floating on the surface. This contains the toxin. It is skimmed off 

 with a spoon, placed in watch-glasses, and these are dried in vacuo and stored 

 in the dark, also in vacua, or in an exsiccator containing strong sulphuric acid. 

 For use the contents of one are dissolved up in a little normal saline solution. 



The comparison of the action of bacteria in the tissues in the 

 production of these toxins to what takes place in the gastric 

 digestion, has raised the question of the possibility of the elabo- 

 ration by these bacteria of ferments by which the process may 

 be started. The problem of toxin formation is thus complicated. 

 Sidney Martin has described toxic albumoses as occurring in all 

 the diseases he investigated, viz., anthrax, ulcerative endocarditis, 

 diphtheria, and tetanus. In each of these cases, therefore, we 

 would be led to suppose that ferments might be produced, 

 which we may look on as the primary toxic agent which acts by 

 digesting surrounding material and producing albumoses which 

 form the secondary poisons. From the standpoint of the bac- 

 terium this process would simply be a preparation of food for 

 further intracellular digestion. Hitherto all attempts at the isola- 

 tion of bacterial ferments of such a nature have failed. 



The question of fermentation has been chiefly discussed with 

 regard to what happens in diphtheria and tetanus. Apart from 

 the fact that a digestive action has occurred, which the presence 

 of albumoses in the body of an animal dead of these diseases 

 affords, the chief available evidence for the existence of ferments 

 lies in this, that the toxic products of the bacteria involved lose 

 their toxicity by exposure to a temperature which puts an end to 

 the diastatic activity of such an undoubted ferment as that of the 

 gastric juice. If a bouillon containing diphtheria toxin be heated 

 at 65 C. for one hour, it is found to have lost much of its toxic 

 effect, and in the case of B. tetani all the toxicity is lost by ex- 

 posure at this temperature. In both diseases there is a still 

 further fact which is adduced in favour of a ferment being con- 

 cerned in the toxic action, namely, the existence of a definite 



