BACILLUS TYPHOSUS 113 



noted. In case this occurs typhoid is present. This agglu- 

 tination reaction is called the Widal test, and is positive in 

 about 95 per cent, of all cases (see Figs. 33 and 34.) 



Cultures. It is also of aid in the diagnosis of typhoid to 

 make a blood culture. This consists in withdrawal, under 

 sterile conditions, of blood from a vein, placing it into suit- 

 able culture medium, and keeping it at body heat in the 

 incubator. If typhoid bacilli be present they will grow so 

 that we may isolate and identify them. The bacilli may be 

 isolated also from the feces and urine during an attack, and 

 as mentioned above, for a long time afterward in the case 



FIG. 36. Typhoid bacilli from nutrient gelatin. X 1100 diameters. 



(Park.) 



of carriers. The methods for isolation are tedious and 

 difficult, and need not be described here. Many technics 

 have been devised to hasten work on epidemics and carriers, 

 but none is as yet perfect. 



The isolation of typhoid bacilli from blood, feces or 

 urine is necessary for a certain diagnosis of the disease 

 in persons who have received antityphoid vaccines, as the 

 prophylactic injections cause the appearance of agglutinin 

 enough to give the Widal reaction. 



Morphology. The typhoid bacillus is a motile rod 2~5Wo to 

 grro incn lon g and 5-0000 to scoop incn wicl e, witn rounded 

 ends, growing in long threads at times. Its motility is due 

 8 



