TETANUS. 241 



developed in the bouillon is exposed over a water-bath 

 for an hour at a temperature of 80 C. (176 F.), and from 

 it a new anaerobic bouillon-culture is made at once. If 

 after several days' development this culture still contains 

 foreign bacteria, anaerobic plates are prepared. 



Immunity and Cure of Tetanus in Animals. The laws 

 of immunity and immunization have been more thoroughly 

 studied in tetanus than in any other disease. The reason 

 for this resides, in the first place, in the exceedingly sharp 

 and certain reaction of animals to tetanus-infection, and, in 

 the second place, in the possibility of testing quantitatively 

 the degree of immunity by means of treatment with the 

 toxic bouillon-filtrate. 



Immunity to a toxic-infectious disease is indicative of 

 proof to intoxication : an animal is protected from infec- 

 tion with tetanus if the tetanus-toxin is incapable of mani- 

 festing its toxic activity within the body of the animal. 

 Animals slightly susceptible (dog, hen) can be further im- 

 munized simply by injection of gradually increasing amounts 

 of tetanus-toxin. Their serum, in the hen, likewise the egg- 

 yolk, also acquires thereby immunizing properties. From 

 the serum of dogs subjected to such preliminary treatment 

 Tizzoni and Cattani have precipitated their so-called anti- 

 toxin by means of alcohol. 



Behring's method of immunization by means of tetanus 

 bouillon-cultures attenuated with iodin trichlorid is applica- 

 ble to the immunization of susceptible animals (mice, rab- 

 bits, horses, sheep). The animals are treated first with 

 a bouillon-culture containing 0.25 per cent, iodin trichlorid, 

 and, finally, with undiluted bouillon, of which the animals 

 smaller at intervals of from three to five days, and larger 

 at intervals of eight days then receive steadily increasing 

 doses, until, finally, they bear quite large amounts of pure 

 toxin. 



A fluid suitable for immunization may be secured also by 

 warming the cultures (Vaillard heats the filtrate at first to 

 60 C 140 F., later to 55 .131 F., and, finally, to 

 50 C. 122 F.) ; further, by addition of iodin-water or 

 of lactic acid to the cultures, by cultivation of the bacilli 

 in thymus-bouillon, etc. 



The serum of immunized animals transmits immunity to 

 animals not previously treated ; the higher the original 

 degree of immunity, the more active is the blood-serum. 

 16 



