TYPHOID BACILLUS 151 



In gelatine stab culture it grows in a thread-like granular line, 

 without producing gas. In neither case is the gelatine liquefied. 

 On agar plates the colonies are not so characteristic, being round, 

 grayish- white, and shining. In milk it grows well, not coagulating 

 it even after boiling, and only a very little acid is produced. On 

 acid potato the growth is characterized by its invisibility, . and 

 this fact is used to differentiate it from other kindred bacteria. The 

 growth is only detected by scratching with a needle. In bouillon 

 it grows uniformly, producing very little acid, and no demonstrable 

 amount of gas. In special media (Hiss's semi-solid media) thread- 

 like colonies are produced, which are characteristic. On Eisner's 

 potato media it produces small granular, glistening points. It also 

 grows characteristically in Capaldi and the Drigalski and Conradi 

 media. 



Invasion of Body. This organism generally invades the body 

 by way of the alimentary tract, in food and water. Flies may infect 

 milk and other foods. Oysters may become infected and cause 

 disease. 



Pathogenesis. It is certainly the cause of typhoid fever. Is 

 found in the stools and urine of the patient, and may be recovered 

 from the blood. Also found in the spleen and gall bladder. It 

 produces well marked histological changes in the lymphoid struc- 

 tures, particularly in Peyer's patches, solitary follicles, and other 

 lymph glands. There is, according to Mallory, a massive endothe- 

 lial proliferation in the lymph glands. This causes occlusion of 

 the lymph vessels, and is followed by necrosis (ulceration) of the 

 Peyer's patches. The intense phagocytic action of the fixed lym- 

 phatic cells in the glands is manifest toward the red blood cells, 

 which are devoured in great numbers. The toxin causes degenera- 

 tion of other organs, particularly in the liver. Bacilli are found in 

 the spleen and blood. The rose colored spots are found to be full 

 of them. The disease is certainly not a merely localized infection 

 of the lymph structures, but is a bacteraemia. There is of ten a 

 mixed infection in which streptococcus pyogenes in the blood 



