592 Typhoid Fever 



portion which shows the yellowish-brown color. The gelatin is not 

 liquefied. 



Gelatin Punctures.— When transferred to gelatin puncture cul- 

 tures, the typhoid bacilli develop along the entire track of the wire, 

 with the formation of minute, confluent, spheric colonies. A small, 

 thin, whitish layer develops upon the surface near the center. The 

 gelatin is not liquefied, but is sometimes slightly clouded in the neigh- 

 borhood of the growth. 



Agar-agar. — The growth upon the surface of obliquely solidified 

 gelatin, agar-agar, or blood-serum is not luxuriant. It forms a thin, 

 moist, shining, translucent band with smooth edges and a grayish- 

 yellow color. 



Potato. — When potato is inoculated and stood in the incubating 

 oven, no growth can be seen even at the end of the second day, 

 but if the surface of the medium be touched with a platinum wire, 

 it is found entirely covered with a rather thick, invisible layer of 

 sticky vegetation which the microscope 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. — In 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. No indol 

 is formed. 



Milk. — In milk containing litmus a very slight and slow acidity 

 is produced, which later gives place to distinct alkalinity. The 

 milk is not coagulated. 



Vital Resistance. — The organisms grow well at all ordinary tem- 

 peratures. The thermal death-point is given by Sternberg at s6°C., 

 destruction being effected in ten minutes. Upon ordinary cultiure- 

 media, the organisms remain alive for several months if drying is 

 prevented. In carefully sealed agar-agar tubes Hiss found the or- 

 ganism still hving 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 lived for six months in the blind terminal of a water- 

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



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

 ders Co., 1900. 



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

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



