ON THE ANTITOXINS OF DIPHTHERIA. 203 



therefore has a weaker antitoxic value, the total amount of 

 antitoxins lost in a lon£ interval of time exceeds that 

 yielded by blood. In a month a goat will yield 30 litres 

 of milk, which corresponds to about ih litres of blood, 

 an amount in excess of what can be taken from the 

 animal in the same time. The antitoxins in milk can 

 be concentrated by Wassermann's method, and employed 

 as a practical therapeutic agent. 



The properties of the blood-serum of animals rendered 

 artificially immune to diphtheria are not exerted upon the 

 bacillus, but upon the toxins of this, both inside and outside 

 the body ; the effect in the organism and in a test-tube is 

 the same. The chemistry of this reaction is not under- 

 stood, but the poison is considered to be neutralised, or its 

 action to be balanced, by bodies spoken of as antitoxins. 

 Quantitative tests show that if a certain amount of anti- 

 toxic serum is sufficient for neutralisation in vitro, an 

 amount at least five times greater is necessary when this 

 is to counteract the same amount of toxin in the body, 

 though it is immaterial whether the introduction of antitoxic 

 bodies takes place at the seat of the injection of toxin or 

 in some other part of the body. In such experiments are 

 the bacilli or the toxins destroyed ? The evidence to 

 decide this is most conflicting. Buchner considers that the 

 poison is not destroyed either inside or outside the body, 

 and when protective substances appear in the blood of 

 immune animals these bodies are themselves introduced 

 with the toxin, or possibly are actually identical with the 

 toxins themselves ; in other words, the condition of ac- 

 quired immunity is specific, and wholly different from 

 natural resistance, a term that should be restricted to such 

 cases as can be noticed in the rat, the blood of which 

 animal possesses no antitoxic substances, and therefore the 

 resistance shown to diphtheria bacilli or toxins must be 

 fundamentally different from acquired immunity (2,3). That 

 the poison is not necessarily destroyed is made clear by the 

 following observation : Guinea pigs are treated with anti- 

 toxic serum after the introduction of a lethal dose of toxin, 

 and these do not succumb, while the same experiment on 



