BACILLUS TYPHOSUS 287 



blue colonies, about 1 to 3 millimeters in diameter. Colonies of the 

 colon bacillus and other members of the colon-typhoid group are 

 larger, coarser, less transparent, and red. To identify the bacilli 

 beyond doubt the small transparent colonies must be tested with an 

 agglutinating typhoid serum. 



Morphology. The typhoid bacillus is a rather plump rod 1 to 3 

 micra in length, 0.5 to 0.8 micron in diameter. It has rounded ends, 

 frequently forms longer or shorter chains, is very actively motile, and 

 possesses numerous long, delicate flagella, but does not form spores. 

 It stains with the ordinary watery anilin stains, but takes them rather 

 slowly, and is best dyed with a watery fuchsin solution; it is Gram 

 negative. 



Cultural Properties. The bacillus grows both in the presence and 

 absence of oxygen, best at blood temperature, well between 25 and 

 ^7 C., poorly below 20 C. It is easily destroyed by antiseptics 

 and by heat. It grows well on all of the ordinary laboratory media and 

 does not liquefy gelatin. On potatoes it generally forms an abundant 

 but invisible growth; occasionally, however, a heavy, yellowish-brown, 

 visible growth. The typhoid bacillus does not form gas from glucose, 

 galactose, or levulose; it does not coagulate milk. 



Formation of Agglutinins and Other Antibodies. When typhoid 

 bacilli are inoculated into animals, or when human beings become 

 infected in a natural way, through drinking contaminated water or 

 otherwise, antibodies which will precipitate, agglutinate, and dissolve 

 typhoid bacilli develop in the blood serum during the course of the 

 disease. In other words, the blood serum then contains specific 

 precipitins, agglutinins, and bacteriolysins. These antibodies appear 

 comparatively early, and for this reason an early and indubitable 

 diagnosis of typhoid fever in man can today, as a rule, be established 

 by the serum test. This very simple test is usually made as a micro- 

 scopic test, and the only elements necessary are some blood from the 

 suspected case and a young, vigorous, typhoid-bacillus culture. The 

 latter is generally raised on slanted agar or glycerin agar in the incu- 

 bator at blood temperature (37 C). It is best to use a culture eighteen 

 hours old for the test; at least it should not be much older than 

 twenty-four hours, because young cultures contain the most vigorous 

 and the most lively bacilli. Blood is obtained by puncturing the 

 cleansed ear or finger tip of the patient with a sharp sterile needle 

 and allowing it to drop (in small drops) on a clean slide, so that the 

 individual drops do not touch but have a certain free space between 

 them. The blood is then allowed to dry on the glass slide, which, if it 

 is not to be used immediately, should be wrapped in a clean piece 

 of paper and protected against moisture and dirt. The test itself 

 can be made at any time from this dried blood. The steps are as 

 follows : 



1. Remove from the agar slant with a platinum loop some of the 

 growth, preferably from the very margin, because the most motile 



