164 A MANUAL OF BACTERIOLOGY 



the two, though not necessarily chemical combination in 

 the strict sense, seems to be proved by the work of Martin 

 and Cherry. Brodie, 1 and Martin and Cherry, 2 making 

 use of a Chamberland filter, the pores of which had been 

 rendered very fine by saturating with gelatin, found that 

 toxin would pass through such a filter but that antitoxin 

 would not, presumably because the molecule of the latter 

 is larger. By mixing diphtheria toxin and antitoxin in 

 such proportion that the latter was in sufficient quantity 

 to neutralise the toxin, and subjecting the mixture to 

 filtration through a gelatin filter, the filtrate was found 

 to be non-toxic. Now since toxin can pass through such 

 a filter, the inference is that the toxin has united with 

 the antitoxin. Using snake- venom and its anti-serum or 

 anti-venin, another method was employed. The anti- 

 venin is destroyed by heating to 68 C. for ten minutes, 

 while the toxic properties of the venom are unaltered by 

 this treatment. By making mixtures of venom and anti- 

 venin, and, after a certain time has elapsed for the inter- 

 action to take place, heating to 68 C. for ten minutes, 

 it was found that the mixture is non-toxic, pointing to the 

 union of the toxin (venom) with the antitoxin (anti-venin). 

 Calmette had performed the same experiment but with 

 a different result, finding his mixtures still toxic after 

 heating. Calmette, however, treated his solutions almost 

 immediately after mixing, and Martin and Cherry point 

 out that a certain time must be allowed to elapse for the 

 interaction to take place, and noted that moderate warming 

 hastens it, as is the case with all chemical interactions. 

 For instance, they found that one mixture of venom and 

 anti-venin allowed to interact for two minutes, five minutes, 

 and ten minutes before heating, killed the animals in 

 thirteen hours, fifteen hours, and twenty- three hours 



1 Journ. of Path, and Bact., 1897, p. 460. 



2 Proc. Roy. Soc. Lond., vol. Ixiii, 1898, p. 420. 



