TETANUS 73 



it is a soluble toxin like diphtheria toxin, and it is estimated that 1/300 

 of a grain is fatal for man. 



Rosenau has established an antitoxin unit for tetanus which has the power of 

 neutralizing one thousand minimal lethal doses. Practically, it is ten times the 

 least quantity of antitetanic serum necessary to protect the life of a 350 grams 

 guinea-pig from a test dose of tetanus toxin furnished by the hygienic laboratory. 

 (The necessity of some definite unit is apparent when tests have shown that serum 

 stated to contain six million units per c.c. only had a value of 90 of the official 

 American units.) Consequently it is a unit ten times as neutralizing as the diph- 

 theria antitoxin one. The antitoxin of tetanus is less efficient than that of diphtheria 

 for the following reasons: 



i. There is about three times as great affinity in vitro between diphtheria toxin 

 and antitoxin as is the case with tetanus. 



FIG. 23. Tetanus bacilli showing end spores. (Kolle and Wassermann.) 



2. The tetanus toxin has greater affinity for nerve cells than for antitoxin. 



3. Treatment with antitoxin is successful after symp.toms of diphtheria appear. 

 With tetanus it is almost hopeless after the disease shows itself. Hence the impor- 

 tance of the early bacteriological examination of material from a suspicious wound 

 (rusty nail). 



4. The tetanus toxin ascends by way of the axis cylinder, and the antitoxin 

 being in the circulating fluids cannot reach it, whereas with diphtheria both toxin 

 and antitoxin are in the circulation. Diphtheria also selects the cells of paren- 

 chymatous and lymphatic organs which are more tolerant of injury than the nerve 

 cells. The dose of tetanus antitoxin as a prophylactic is 1500 units; as a curative 

 agent 5000 to 20,000 units. Recent experience shows that it should be injected 

 intravenously when symptoms have manifested themselves. 



That the disease is due to toxin is shown not only experimentally, but also if 

 spores are carefully freed of all toxin by washing, and then introduced they do not 

 cause tetanus the polymorphonuclears engulfing them. The importance of the 



