232 



ANTITOXINS 



It was soon discovered that toxins are unstable compounds, and that, 

 almost immediately after their production, they begin to change into 

 toxoids, which are not acutely poisonous, but which retain their power 

 to neutralize antitoxin. 



In order to standardize a serum it is necessary that the strength of 

 the toxin be known, and since this is so variable, a standard antitoxin is 

 supplied by the Hygienic Laboratory, by which the various antitoxin 

 plants may measure the strength of their toxins. By mixing varying 

 quantities of toxin with one unit of this standard antitoxin and injecting 

 these into 250-gram guinea-pigs, the L + (limes death) dose is obtained, 

 which is the dose of toxin required to kill a pig in four days with the one 

 unit of antitoxin. In order accurately to determine this dose many 

 pigs may be required, but this method of titration is the key-note to 

 successful standardization. 



Such a titration for instance, has shown a toxin to react as follows : 



TABLE 1. METHOD OF DETERMINING THE L+ DOSE OF DIPH- 

 THERIA TOXIN 



One antitoxin unit +0.2 c 

 +0.22 

 +0.24 

 +0.25 

 +0.26 

 +0.28 

 +0.3 

 +0.32 

 +0.34 

 +0.35 



c. toxin = No visible symptoms. 

 = No symptoms. 



= Usually no symptoms or a very slight reaction. 

 = Very slight congestion and edema. 

 = Slight edema at site. 

 = Edema; sometimes late paralysis. 

 = Acute edema and sometimes death. 

 = Always acute death about the fourth day. 

 = Death from second to third day. 

 = Death about the second day. 



Here the L+ dose is 0.32 c.c. The dose of toxin that just neu- 

 tralizes the antitoxin without causing symptoms has been called by 

 Ehrlich the L6 (limes zero) dose, and in this instance it is about 0.24 c.c. 

 This determination, however, has not the same practical value as the 

 L+ dose. 



Having determined the L+ dose of the toxin, a series of six to eight 

 guinea-pigs are injected with this constant dose of toxin and increasing 

 amounts of the corresponding antitoxin serum; for instance, No. 1 

 would receive 0.001 c.c. of serum; No. 2, 0.002 c.c.; No. 3, 0.003 c.c.; 

 No. 4, 0.004 c.c.; No. 5, 0.005 c.c.; No. 6, 0.006 c.c., etc. If at the end 

 of the fourth day Nos. 1, 2, 3, and 4 were dead and Nos. 5 and 6 were 

 alive, the serum would contain 200 units of antitoxin in a cubic centi- 

 meter. Thee injections are best given with precision syringes, the one 

 devised by Kitchens being particularly serviceable (Fig. 71). The syr- 

 inges are sterilized, and the needles are dipped in sterile vaselin to 



