1 66 LECTURES ON IMMUNITY 



by formaldehyde, hydrogen peroxid, or strong alcohol. 

 In this case the reagents often display the phenomenon 

 that a greater dosage does not agglutinate, whereas a 

 lesser dose produces the effect. Acetic acid does not 

 agglutinate some cholera vibrios if it be used in a concen- 

 tration of o.i per cent, but has a strong agglutinating 

 effect in solutions of 10 per cent only to lose it again at 

 a strength of 50 per cent, according to the experiments of 

 Bossaert. Mercuric chlorid agglutinates in a concentra- 

 tion of only 0.3 per cent and safranin or vesuvin are active 

 at a concentration of 0.05 per cent. Even in this case 

 different bacilli are sensitive to a different degree; thus, 

 for instance, typhoid bacilli are more than ten times as 

 sensitive to safranin as colon bacilli. 



If the action of the agglutinin be a coagulation of the 

 contents of the bacilli, it is easy to understand how other 

 coagulating substances, such as alcohol, acids, or ura- 

 nium acetate, may change the properties of the bacilli in 

 nearly the same manner as the specific agglutinin, as 

 results from the experiments of Bechhold cited above. 

 The agglutinins are therefore probably only a special class 

 of precipitins, which they in many cases even resemble 

 in showing optima of action at a certain concentration. 



