BACILLUS TYPHOSUS 



123 



more bacteriolysin than is possessed by the blood of 

 a person who has never suffered from typhoid. 



Widal Test. Far more important antibodies are 

 the aggliitinins used extensively in the diagnosis of 

 the disease. These are bodies in the blood which 

 when brought into contact with the bacilli, make them 

 stop moving and clump together. To use this for 

 diagnostic purposes a fluid culture or salt solution sus- 



FIG. 35. Microscopic field, showing the top of a drop with the 

 typhoid reaction. (Park.) 



pension of the living, actively motile germ is prepared. 

 Some blood from the patient is obtained, the clear 

 serum collected and mixed with the bacterial suspen- 

 sion in dilution of 1 part of the serum to 20, 50, 100 or 

 more parts of the bacterial suspension. These dilutions 

 are used because sera from some persons entirely free 

 from typhoid will clump the bacilli in low dilution, 1 

 to 5 or 1 to 10. The mixture of serum and bacteria is 



