376 



MANUAL OF BACTERIOLOGY. 



M. W. Richardson has devised an application of the serum-test to plate- 

 colonies suspected of containing typhoid bacilli. If a typhoid colony be torn 

 with a needle, under moderate magnification "a seething motion resembling 

 much the appearance of a swarm of bees" may be seen. This appearance is 

 due to the motility of the bacteria. If such a colony be touched with a small 

 quantity of blood-serum from a case of typhoid fever, the motion is said to cease 

 instantly and almost absolutely. Colonies of other motile bacteria do not 

 undergo a corresponding loss of motility. 



THE SERUM-TEST FOR TYPHOID FEVER.* 



When a small quantity of a culture of typhoid bacilli is mixed with a little 

 blood-serum derived from a case of typhoid fever, within a few minutes the 

 motility of the typhoid bacilli ceases and they become agglutinated into clumps 



FIG. 97. Application of the serum-reaction to typhoid bacilli. A shows 

 the distribution of the bacilli before the reaction. It is to be remembered that 

 they are motile and their positions may change continually. B shows clump- 

 ing of the motionless bacilli after mixture with the serum of a case of typhoid 

 fever. (Diagrammatic.} 



or masses (see Agglutinins, Bacterial Poisons, page 190). The bacilli may 

 eventually undergo disintegration into granular material (see Lysins, Bacterial 

 Poisons, page 193). This reaction rarely takes place with the blood-serum 

 of healthy persons or of those suffering with other diseases, nor when the blood- 

 serum of a typhoid fever case is mixed with motile bacteria other than typhoid 

 bacilli: It has been observed in the blood-serum of an infant born while the 

 mother was convalescing from typhoid fever. 



The agglutinating substance has been found in blister-serum and in the 

 milk of typhoid cases, in fluids from the serous cavities and inflammatory and 

 edematous areas in variable amounts, and occasionally in urine, bile and tears. 



The reaction may be obtained by adding blood-serum to a young bouillon- 

 culture of typhoid bacilli kept in the incubator, when the occurrence of agglutina- 



*This test is often known as the " Widal reaction." For a history and general 

 discussion of the subject see Durham. Journal of Experimental Medicine. 

 Vol. V. p. 353. 



