FORMATION OF AGGLUTININS 281 



independent of Widal, but, owing to a lack of patients, Widal preceded 

 him in the publication of a more extensive work. 



At the present time this diagnostic reaction is known as the Gruber- 

 Widal reaction. It has proved of great value to a large number of dif- 

 ferent investigators, not only in making the serum diagnosis of typhoid 

 fever, but in other infections as well. 



Normal and Immune Agglutinins. Normal serums are frequently 

 capable of agglutinating bacteria, such as the typhoid, colon, pyocy- 

 aneus, and dysentery bacilli. In some cases the typhoid bacillus may be 

 agglutinated in dilutions as high as 1 : 30, a point of practical impor- 

 tance in the clinical use of the test. When a normal serum is found to 

 have a high agglutinating power, it is probable that 

 a previous infection by the microorganism has oc- 

 curred. Since the serum of a new-born child is 

 largely devoid of agglutinins that are found in later 

 life, the so-called normal agglutinins may, after all, 

 be acquired properties. 



The term immune agglutinin is applied to the 



RETIC STRUO 

 agglutmatmg substance in a serum developed as the TURE OF AGGLU- 



result of infection or of systematic immunization SAJTCNOTO' AG ~ 

 with the microorganism. 1, Agglutinin: 



Formation of Agglutinins. According to Ehr- ap P 



unon 



lich's side-chain theory, agglutinins are antibodies of with antigen; 4, the 



i i /TT .fOA r agglutinophore or 



the second order (Fig. 78). They resemble antitoxins zymophore group. 



or receptors of the first order in possessing an affinity- 2j Agglutinoid. 



J Same structure as 



bearing or haptophore group that unites with the agglutinin, except 



antigen, but they differ from them in having also a phore^r zymophore 

 functional or agglutinophore group that agglutinates g rou P is lost - 

 the antigen when this union has occurred (Fig. 79). 



Agglutinins that have lost their zymophore or agglutinophore group 

 through the action of heat, age, acids, etc., but that still possess their 

 haptophore group, are called agglutinoids, just as toxins that have lost 

 their toxophore group are called toxoids. Such agglutinoids, then, may 

 still combine with the bacteria or blood-cells without being able, how- 

 ever, to produce agglutination (Fig. 80). 



It is found, at times, that even a fresh serum, when concentrated, 

 will cause less agglutination than when it is diluted. This is ascribed to 

 the presence of agglutinoids, which have a stronger affinity for agglutin- 

 ogen than has the agglutinin. When producing a reaction of this char- 

 acter they are called pro-aqglutinoids. When the serum is diluted, the 



