632 Typhoid Fever 



typhoid patients during the second and third weeks of the 

 disease. 



Cultivation. — The bacillus grows well upon all culture-media 

 under both aerobic and anaerobic conditions. 



Colonies.— The deep colonies upon gelatin plates appear under the 

 microscope of a brownish-yellow color and spindle-shape, and are 

 sharply circumscribed. When superficial, however, they become 

 larger and form a thin, bluish, iridescent layer with notched edges. 

 The superficial colonies are often described as resembling grapevine 

 leaves in shape. The center of the superficial colonies is the only 

 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 Hquefied, but is sometimes shghtly clouded in the neigh- 

 borhood of the growth. 



Agar-agar. — The growth upon the surface of obUquely sohdified 

 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 tj^hoid baciUus 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 htmus 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 culture- 

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

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



