THE AGGLUTINATION REACTION 289 



3. The patient may have a mixed infection of typhoid and para- 

 typhoid, and therefore agglutinin for both may be present. Saturation 

 of the serum with typhoid bacilli will remove the typhoid and probably 

 a small portion of the paratyphoid agglutinin. After tHis reaction the 

 serum will still show the presence of a decided quantify of paratyphoid 

 agglutinin. 



In selecting the most likely one of these hypotheses a decision may be 

 reached by adopting the method of Castellani (Citron), which is as fol- 

 lows: 



1. Four rows of test-tubes are arranged, each row being made up of 

 four small tubes each containing 1 c.c. of serum dilutions 1 : 20, 1 : 40, 

 1 : 80, and 1 : 160 respectively. 



2. In each of the tubes of the first and second rows five loopfuls of 

 typhoid bacilli are emulsified. An extra tube containing 1 c.c. of nor- 

 mal salt solution receives a similar amount of bacteria, and serves as the 

 typhoid control. 



3. In each tube of the third and fourth rows five loopfuls of para- 

 typhoid bacilli are emulsified. Arrange the paratyphoid culture control. 



4. Mix gently and incubate for four hours. Carefully record the 

 presence or absence of agglutination in each test-tube. Centrifuge all 

 the tubes excepting the two controls, and transfer the supernatant fluid 

 of each to other test-tubes arranged in the same order. 



5. To each tube of the first and third rows add five loopfuls of ty- 

 phoid bacilli; to each of the second and fourth rows, five loopfuls of 

 paratyphoid bacilli. Mix well and incubate for four hours. 



(a) If typhoid is present, the agglutination titer in the first part of 

 the test will be strong in the tubesU the first and second rows, and weak 

 in those of the second and third rows. In the second part of the test the 

 titer for typhoid will be weak or nil in the first, second, and fourth rows, 

 whereas in the third row it will remain practically the same. 



(6) If paratyphoid exists, the agglutination titer in the first part of 

 the test will be strong in the tubes of the third and fourth rows, and weak 

 in those of the first and second rows. In the second part of the test the 

 titer for paratyphoid will be less or nil in the fourth row, and strong or 

 unchanged in the second row. 



(c) If a mixed infection exists, the agglutination titer in the first part 

 of the test will be strong in the tubes of all four rows. In the second 

 part of the test the titer in the first and fourth rows is much weaker or 

 nil, and in the second and third rows it will remain the same. 



19 



