CASTELLANl'S TEST. 103 



agglutinin number i, and with paratyphoid bacilli through its agglutinins 

 numbers i and 2. The other "partial agglutinins" remain inactive on 

 account of the missing suitable agglutinogens. 



The existence of such partial antigens and partial antibodies is, for some 

 bacteria more than of mere theoretical importance. It is even possible that 

 a strong colon serum will agglutinate no colon bacilli other than that partic- 

 ular strain employed for the production of the serum. Such being the 

 case with a number of micro-organisms, the sera made at present both for 

 diagnostic and therapeutic purposes are polyvalent (multipartial). By 

 polyvalent serum is meant one which is produced either by immunizing 

 animals with many different strains of the same bacterium, or a mixture of 

 sera obtained from different animals immunized with various strains. 



The practical importance of partial agglutinins is recognized 

 Castellani's in the diagnosis of mixed infections. Castellani found that by 

 Test. the mixture of an immune serum with its corresponding bac- 

 teria, the agglutinins for these as well as the partial agglu- 

 tinins for the heterologous bacteria are absorbed. On the other hand, if the 

 same serum be mixed with the heterologous bacteria, the agglutinins for the 

 homologous group are quantitatively retained. 



A practical example will make this clearer. 



The serum of a patient agglutinates typhoid as well as paratyphoid bacilli, in a dilu- 

 tion of i : 100. This may indicate one of three possibilities: 



a. Patient is infected with typhoid, but has formed an exceptionally large number of 

 partial-agglutinins for paratyphoid bacilli. 



b. Patient is infected with paratyphoid bacilli, but has formed at the same time many 

 partial-agglutinins for typhoid. 



c. Patient has a mixed infection of typhoid and paratyphoid and therefore formed 

 agglutinins for both. 



A decision in regard to the above may be reached according to the following method 

 given by Castellani: 



Four rows of test tubes are arranged, each row containing three tubes with i c.c. of 

 serum dilutions i : 10, i : 50, i : 100 respectively. In each of the first and second row, 

 i loopful of typhoid bacteria is emulsified. 



In each of the third and fourth row, i loopful of paratyphoid B. bacilli is emulsified. 

 The tubes are placed into the incubator for two hours, absence or presence of agglu- 

 tination in each test-tube noted, and after centrifugalization (which may become unneces- 

 sary if the bacteria are strongly clumped or grouped at the bottom of the tube), the super- 

 natant liquid is transferred into other test-tubes and kept in the same order. 

 Then each of the first row receives i loopful of typhoid bacilli, 



each of the second row receives i loopful of paratyphoid B. bacilli, 

 each of the third row receives i loopful of typhoid bacilli, 

 each of the fourth row receives i loopful of paratyphoid B. bacilli, 

 All are once more placed into the incubator for two hours. 



a. If typhoid exists, the agglutination titer in the second part of the test will become 

 weaker in the first, second and fourth rows, while that in the third row remains 

 the same. 



b. If paratyphoid exists, the titer for typhoid in the first and third row becomes less, 



