288 AGGLUTININS 



ture control. A microscopic examination of a deposit will show that 

 the bacilli point in all directions, whereas in a deposit of unagglutinated 

 bacilli they lie horizontally side by side. 



When agglutinoids are present, agglutination is absent or incomplete 

 in the lower dilutions of serum, and complete in the tubes containing the 

 higher dilutions. This is called pro-agglutination (Fig. 83). 



Readings are facilitated by the use of a special instrument known as 

 the agglutinoscope (Fig. 84). The tubes are placed in a rack having 

 numbered holes, and are viewed from beneath with the aid of a mirror. 

 In this way one looks upward through the column of fluid, and secures a 

 combined view of sediment and turbidity, and when examined with the 

 culture control, fine and accurate readings may be made. 



The method of Kolle and Pfeiffer is very convenient, and may be 

 safer than that of adding live cultures with a pipet. It is conducted as 

 follows : 



1. Make dilutions of serum as described. 



2. Emulsify thoroughly a loopful (2 mg.) of culture from an eighteen- 

 to twenty-four-hours-old agar culture in the first test-tube, repeating 

 the process in the second tube, and so on through the series. In this 

 method the serum dilutions are not doubled; thus in the foregoing series 

 the dilutions would be 1 : 10, 1 : 20, 1 : 40, 1 : 80, 1 : 160, 1 : 320. 



3. The tubes are gently shaken, labeled, plugged, and incubated as 

 directed in the preceding method. 



TECHNIC OF THE ABSORPTION AGGLUTINATION TEST IN MIXED INFECTION 

 (THE SATURATION TEST OF CASTELLANI) 



The practical importance of partial agglutinins is recognized in the 

 diagnosis of mixed infections. Thus the serum of a patient may agglu- 

 tinate typhoid as well as paratyphoid bacilli in dilutions up to 1 : 100. 

 This may indicate one of three possibilities: 



1. The patient may be infected with typhoid, but has formed an 

 exceptionally large quantity of group agglutinins for paratyphoid bacilli. 

 Saturation of this serum with typhoid bacilli will remove all the typhoid 

 and a portion, if not all, of the group agglutinins. Saturation with para- 

 typhoid bacilli will remove the group agglutinins, but not the main or 

 typhoid agglutinin. 



2. The patient may be infected with paratyphoid bacilli, but has 

 formed, at the same time, many partial agglutinins for typhoid bacilli. 

 Saturation of the serum with paratyphoid bacilli will remove all the 

 paratyphoid and a large portion of the typhoid agglutinin. 



