Metabolic Products 633 



ganism still living after thirteen years. According to Klemperer and 

 Levy,* the bacilli can remain vital for three months in distilled water, 

 though in ordinary water the commoner and more vigorous sapro- 

 phytes outgrow them and cause their disappearance in a few days. 

 There seems to be some doubt, however, on this point, as Tavelf 

 found that it hved for six months in the blind terminal of a water- 

 supply pipe, and Hofmann,J after planting it in an aquarium con- 

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

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

 tom after two months. In elaborate experimental studies of this 

 question Jordan, Russel, and Zeit§ found its longevity to be only 

 iree or four days under conditions resembling as nearly as possible 

 those found in nature. When buried in the upper layers of the soil 

 the bacilU retain their vitality for nearly six months. Robertson |1 

 found that when planted in soil and occasionally fed by pouring 

 bouillon upon the surface, the typhoid bacillus maintained its vitality 

 for twelve months. He suggests that it may do the same in the soil 

 about leaky drains. 



Cold has little effect upon t5^hoid bacilli, for some can withstand 

 freezing and thawing several times. Observing that epidemics of 

 typhoid fever have never been traced to polluted ice, Sedgwick and 

 Winslow** made some investigations to determine what quantitative 

 reduction might be brought about by freezing, and accordingly ex- 

 perimentally froze a large number of samples of water intentionally 

 infected with large numbers of t3^hoid bacilli from different sources. 

 It was found that the bacilli disappeared in proportion to the length 

 of time the water was frozen, and that the reduction averaged 99 per 

 cent, in two weeks. The last two or three bacilli per thousand 

 appeared very resistant and sometimes remained aUve after twelve 

 weeks. 



The typhoid bacillus resists the action of chemic agents rather 

 better than most non-sporogenous organisms. The addition of 

 from 0.1 to 0.2 per cent, of carboHc acid to the culture-media is 

 without effect upon its growth. At one time the tolerance to carbolic 

 acid was thought to be characteristic, but it is now known to be 

 shared by other bacteria (colon bacillus). It is killed by 1 : 500 bi- 

 chlorid of mercury solutions and 5 per cent, carbolic acid solutions in 

 five minutes. 



Metabolic Products. — The typhoid bacillus does not produce indol. 

 It produces a small amount of lactic and formic acids when grown in 

 sugar-containing media, but its regular tendency is to form alkalies 



* " Clinical Bacteriology." Translated by A. A. Eshner, Phila., W. B. Saun- 

 ders Co., IQOO. 



f'Centralbl. f. Bakt. u. Parasitenk.," 1903, xxxvin, p. 166. 



t';Archiv. f. Hyg.," 1905, in, 2, 208. 



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



II "Brit. Med. Jour.," Jan. 8, 1898. 



* "Jour. Boston Soc. of Med. Sci.," March 20, 1900, vol. iv, No. 7, p. 181. 



