412 THE QUESTION OF IMMUNITY AND ANTITOXINS 



such union is the mode of antagonism.* The progress of disease 

 is, therefore, a struggle between the toxins and the antitoxins: 

 when the toxins are in the ascendency we have an increase of 

 the disease ; when the antitoxins are in the ascendency we have a 

 diminution of disease. If the toxins triumph, the result is death; 

 if the antitoxins and resistance of the tissues triumph, the result 

 is recovery. 



Different Kinds of Immunity. — We have gathered, then, that 

 whenever bacteria, introduced into the blood and tissues, fail to 

 multiply or produce infection (as in saprophytic bacteria, or in 

 immunity of a particular animal from a specific microbe), this 

 inability to perform their rdk is brought about by some property 

 in the living blood serum which opposes their life and action; 

 and further we have seen that this protective property is ex- 

 haustible according to the number of bacteria, and differs with 

 various species of bacteria, and in different animals. Buchner 

 designated these protective bodies, held in solution in the blood, 

 alexines, and regarded them as belonging to the albuminous bodies 

 of the lymph and plasma. Alexines are naturally produced anti- 

 toxins; ordinary antitoxins are acquired alexines. Hence we have 

 the well-known terms " natural " and " acquired " immunity. Of the 

 former we have already spoken. The latter, acquired immunity, is 

 a protection not belonging to the tissues of individuals naturally and 

 as part of their constitution, but it is acquired during their lives as 

 a further protection of the tissues. This may happen in one, or 

 both, of two ways. Either it may be an involuntary acquired 

 immunity, or a voluntary acquired immunity, a natural attack of 

 disease, or an artificial attack due to inoculation. Small-pox, typhoid 

 fever, even scarlet fever, are diseases which rarely attack the same 

 individual twice. That is because each of these diseases leaves 

 behind it, so to speak, its antitoxic influence. Hence the individual 

 has involuntarily acquired immunity against these diseases. An 

 example of voluntary acquired immunity is also at hand in the old 

 method of preventive inoculation for small-pox, or variolation. This 

 was clearly an inoculation setting up an artificial and mild attack 

 of small-pox, by which the antitoxins of that disease were produced, 

 and protected the individual against further infection of small-pox ; 

 that is to say, it was a voluntary acquired immunity. This form of 

 artificial production of protection is artificial immunity. It may be 



* Ehrlich has shown that the antitoxic power of these anti-bodies varies widely, 

 and is not uniform. Moreover, antitoxins are specific in their action. He suggests 

 that the ultimate toxin molecule contains two unsatisfied affinities, one of which can 

 combine with antitoxin (haptophorous), and the others having a toxic action 

 (toxophorous). These groups under certain conditions can lose none of their combin- 

 ing power, the toxophorous being more readily weakened than the haptophorous. 

 The weakened toxins are termed toxoids or toxones. 



