360 



THE BACILLUS OF TYPHOID FEVER. 



FIG. 111. Single colony of Bacillus 

 typhi abdominalis, in nutrient gela- 

 tin, (x?) From a photograph by 

 ROUT. 



In gelatin plate cultures small, white colonies are developed at 



the end of thirty-six to forty-eight hours, which under the microscope 



are seen to be somewhat irregular in 

 outline and of a spherical, oval, or long- 

 oval form ; these have by transmitted 

 light a slightly granular appearance and 

 a yellowish-brown color. At the end of 

 three or four days the colonies upon the 

 surface of the gelatin form a grayish- 

 white layer of one to two millimetres in 

 diameter, with more or less irregular 

 margins, and, when developed from deep 

 colonies, with an opaque central nucleus. 

 These colonies, by transmitted light, 

 have a yellowish-brown color towards 

 the centre, where they are thickest, 



while the margins are colorless and transparent ; the surface is com- 



monly marked with a network of lines and furrows. Stick cultures 



in ten-per-cent gelatin, at 18 to 20 C., at the 



end of three days show upon the surface a 



whitish, semi-transparent layer, with sharply 



defined margins and irregular outline, which 



has a shining, pearly lustre ; and along the 



line of puncture a grayish- white growth, made 



up of crowded colonies, which are larger and 



more distinct at the bottom of the line of growth. 



Upon nutrient agar, at a temperature of 35 



to 37 C., the growth is more rapid and forms 



a whitish, semi-transparent layer. The cul- 



tures give off a faint putrefactive odor. The 



growth upon blood serum is rather scanty, in 



the form of transparent, shining patches along 



the line of inoculation. 



The typhoid bacillus develops abundantly 



in milky in which fluid it produces an acid re- 



action ; it also grows in various vegetable in- 



fusions and in bouillon. 



None of the above characters of growth 



are distinctive, as certain common bacilli found 



in normal faeces present a very similar appear- 



anre U'hrri cultivated in tho same media. 



The growth of this bacillus upon potato is 

 an important character, as was first pointed out 

 by Gaffky, In the incubating oven at the end of forty-eight hours, 



FIG m ._ Bacillua typh i 



abdominalis; stick culture 



