june3. i9i8 Destruction of Tetanus Antitoxin 487 



Laboratory had slightly changed the definition, as follows (from a 

 typewritten statement) : 



The test dose of the tetanus toxin F is 0.0007 gram. This should kill a 350-gram 

 guinea pig in about 96 hours, when mixed with one-tenth unit of antitoxin. The 

 test dose contains approximately 100 minimal lethal doses. 



According to this definition, the antitoxin is now the standard from 

 which the toxin is derived, and it is not immaterial whether the guinea 

 pig is alive or dead after 96 hours — the o. i unit as later defined specifies 

 that the guinea pig shall not live more than 96 hours if the dose contain 

 but 0.1 unit. Either definition used consistently would undoubtedly 

 lead to the same conclusions in this work, since these are based upon 

 comparisons made under similar conditions rather than upon absolute 

 values. The older definition was used, as it seemed to be more con- 

 venient. All doses of antitoxin which protected a guinea pig for 96 

 hours were regarded as containing at least o.i unit. There was generally 

 little need for fine distinctions, as few of the guinea pigs died just before 

 the 96-hour limit. With few exceptions these guinea pigs were regarded 

 as having received less than o.i antitoxic unit, according to the older 

 definition. In the following statement the number of guinea pigs that 

 died before the time indicated is shown. All of them had received the 

 test dose of toxin plus varying amounts of antitoxin. Twelve guinea 

 pigs that received only 2 MLD are not included. 



Number of 



Time after inoculation : ^'dead!'^ 



20 to 24 hours 24 



25 to 48 hours 13 r 



49 to 72 hours 36 



a 191 



73 to 96 hours 19 



97 to 120 hours 17 



121 to 144 hours 9 



145 to 168 hours 3 



169 to 192 hours I 



Total 240 



Calculation op the percentage of the total antitoxin de- 

 stroyed. — It will be noticed in Table V that the three guinea pigs (and 

 three others) that received a quantity of serum 374 containing 0.07 

 unit were protected for more than 96 hours against the test dose of toxin. 

 Consequently the quantity of serum calculated to contain 0.07 unit, 

 on the basis of the manufacturer's statement that the serum contained 

 202 units per cubic centimeter (see Table II) actually contained at least 

 O.I unit, the manufacturer apparently having liberally understated the 



a Dead in 73 hours. 

 56112"— 18 2 



