TYPHOID BACILLUS 363 
temperature is required to kill them when they are suspended in 
organic matter, as feces. Cultures exposed to temperatures from 0° 
C. to —10° C. for three months occasionally contain viable organisms. 
Alternate freezing and thawing is more fatal than simple freezing. 
The typhoid bacillus dies out rather rapidly in potable water, less 
rapidly in sterilized potable water. The addition of organic matter, 
particularly of fecal origin, appears to promote longe\'ity somewhat. 
The observations of Jordan, Russell and Zeit^ would indicate that a 
large percentage of organisms exposed in potable water die within 
three days. Kersten^ has shown that typhoid bacilli will develop 
with considerable rapidity in raw milk. The bacilli may remain alive 
in soil for several months, provided they are shielded from flirect 
sunlight, and they may resist drying under similar conditions for 
several weeks. A maximum exposure of from four to eight hours 
to direct sunlight in the months of June, July and August (Northern 
Hemisphere) usually kills the organisms. Mercuric chloride 1 to 1000 
Fig. 51. — Bacillus typhosus, bouillon culture. X 1000. 
kills the naked germs in about ten minutes; 5 per cent carbolic acid 
kills them in from five to ten minutes, as a rule. 
Products of Growth.— The typhoid bacillus liberates small amounts 
of ammonia from jjrotein in sugar-free media, and forms small amounts 
of non-volatile alkaline products as well. The reaction, therefore, 
becomes progressively alkaline. A radical change in the nature of 
the products of metabolism occurs when the bacilli are grown in 
protein media containing utilizable carbohydrates, as glucose or 
mannitol. The reaction becomes strongly acifl, due to the fermenta- 
ticm of the sugar. The protein under these conditions is left unattacked 
except for minute amounts necessary to supply the nitrogenous require- 
ments of the organism. The acids formecl are chiefly lactic acid, 
together with smaller amounts of acetic and formic acid.' Indol or 
1 Jour. Infec. Dis., 1904, 1, 641. 2 Arb. a. d. kais. Gesamt., 1909, 30, .'Ml. 
3 Kendall: Jour. Med. Res., 1911, 24, 411; 1912, 25, 117; Boston Med. and Surg. 
Jour., 1911, 164, 288. Kendall and Haner: Jour. Infec. Dis., 1922, 30, 225. 
