636 Typhoid Fever 



surface of the medium be touched with a platinum wire, it 

 is found that its entire surface is covered with a rather 

 thick, invisible layer of a sticky vegetation which the mi- 

 croscope shows to be made up of bacilli. This is described 

 as the invisible growth. Unfortunately, it is not a constant 

 characteristic, for occasionally a typhoid bacillus will show 

 a distinct yellowish or brownish color. The typical growth 

 seems to take place only when the reaction of the potato 

 is acid. 



Bouillon. Jn bouillon the only change produced by 

 the growth of the bacillus is a diffuse cloudiness. Rarely a 

 pellicle is formed. When sugars are added to the bouillon 

 the typhoid bacillus is found to form acid from dextrose, 

 levulose, galactose, mannite, maltose, and dextrin, but not to 

 form acid from lactose or saccharose. No gas is formed in 

 the fermentation tube with any of the sugars. 



Milk. In milk containing litmus a very slight and slow 

 acidity is produced, which later gives rise to a distinct alka- 

 linity. The milk is not coagulated. 



Vital Resistance. The organisms grow well at all 

 ordinary temperatures. The thermal death-point is given 

 by Sternberg as 56 C., destruction being effected in ten 

 minutes. Upon ordinary culture-media, the organisms re- 

 main alive for several months if drying is prevented. In 

 carefully sealed agar-agar tubes Hiss found the organism 

 still living after thirteen years. According to Klemperer and 

 Levy,* the bacilli can remain vital for three months in dis- 

 tilled water, though in ordinary water the commoner and 

 more vigorous saprophytes outgrow them and cause their dis- 

 appearance in a few days. There seems to be some doubt, 

 however, on this point, as Tavelf found that it lived for 

 six months in the blind terminal of a water-supply pipe, 

 and Hofmann, { after planting it in an aquarium containing 

 fish, snails, water-plants, and protozoa, was able to recover 

 it from the water after thirty-six days, and from the mud 

 in the bottom after two months. In elaborate experimental 

 studies of this question Jordan, Russell, and Zeit found 

 its longevity to be only three or four days under conditions 



*" Clinical Bacteriology." Translated by A. A. Eshner, Phila.j 

 W. B. Saunders Co., 1900. 



t "Centralbl. f. Bakt. u, Parasitenk.," xxxm, p. 166, 1903. 



t "Archiv. f. Hyg.," 1905, LII, 2, 208. 



"Journal of Infectious Diseases," 1904, i, p. 641. 



