TOXINS AND ANTITOXINS 57 



which kills a pig of 350 grams in four to five days. The antitoxic 

 unit is ten times the amount of antitoxin necessary to protect 

 against 100 minimum lethal doses. 



In man the symptoms appear, as a rule, first in trismus of the jaw 

 muscles, but in experimental animals the first spasms are near the 

 injection site when the toxin has been given subcutaneously or 

 intramuscularly. For demonstration purposes the dried toxin is 

 freshly dissolved and five minimum lethal doses injected into the 

 thigh muscles of one hind leg of a guinea-pig. In the course of 

 about two days the leg is found stiff and extended, the animal show- 

 ing excitable reflexes. In the course of another day a sudden noise 

 or other stimulus will excite convulsions, and later the animal will 

 be found in tonic spasm and dies with all four extremities in exten- 

 sion. If the toxin is given intravenously or intraperitoneally, the 

 first symptoms are excitable reflexes, then general clonic and finally 

 tonic spasm. If given intracerebrally, the onset is by epileptiform 

 convulsions. Rabbits are much more resistant to the toxin, and 

 an intravenous injection will lead to gradual wasting and a cachectic 

 death, which has been called " tetanus sine tetano." The suscep- 

 tibility of animals varies with the temperature of the body. Cold- 

 blooded and hibernating animals are resistant at cold winter 

 temperatures, but become susceptible at summer temperatures. 



Tetanolysin. The tetanolysin is easily demonstrable in a toxin. The best 

 red blood-cells for use are those of the goat, sheep and horse. The fol- 

 lowing protocol will show the method of titrating the tetanolysin. The toxin 

 is dissolved so as to make a i per cent, solution in saline, and is further diluted 

 for the experiment 1-2, 1-5, i-io, 1-20. The blood-cells are washed three 

 times and suspended in salt solution so as to make a 5 per cent, solution. For 

 method of washing red blood-cells see page 118. 



Tube 



i 



2 



3 

 4 



5 



The mixtures are incubated in a water bath at 37 for one hour. 



The minimum lytic dose in the above instance is I c.c. of a 1-5 dilution of 

 the i per cent, toxin solution. This is used as the unit to determine the 

 antitetanolysin in an antitetanic horse serum as in the following protocol: 



*Add the sheep cells after the mixture of toxin and serum has been incubated for one-half 

 hour and then incubate one hour. For method of diluting serum so as to obtain required 

 strengths see page 84. 



