21 



on the suriace, which is easily broken and then smks in shreds to the bottom 

 of the tube. The culture has a very disagreeable, sweetish odor. Old cul- 

 tures are always very alkaline. Very old cultures become completely sedi- 

 mented. and brown in color. Growth occurs in slightly alkaline or acid bouil- 

 lon, and small lumps appear in the sediment. 



Milk Cultures. In four days, the milk coagulates into a soft curd with 

 a tihin layer of turbid, yellowish-grey serum on the surface. The reaction is 

 slig-htly alkaline, and the curd digests slowly, as it takes about four weeks for 

 the curd to completely dissolve. Tbe liquid is turbid, yellowish-grey in color 

 somewhat thick, and with an alkaline reaction. There is usually a thick, grey- 

 ish-white sediment. The culture has a disagreeable odor. 



On Potatoes, the roup bacillus develops fairly well, as a thm, grey, 

 smooth and shiny layer. 



In Dunham's solution, a uniform turbidity appears. At the bottom, a 

 grey, flocky sediment forms. After three or four weeks the culture is dark 

 brown, very alkaline, and has a putrid odor. 



T per cent, solution of Peptone with 4 per cent. Dextrose. In this 

 medium, a copious, diffuse turbidity forms, as well as a granular sediment. 14 

 per cent, of gas collects in 48 hours. The reaction is slightly acid, and re- 

 mains so. 



Temperature relations. The roup bacillus grows best at a temperature of 

 37-40 degrees C, and it also grows well at room temperatures. 20-22 degrees C. 



The thermal death-point (Sternberg's method) is 65 degrees C. for to 

 minutes. 



Oxygen requirements. It grows best aerobically. Anaerobic cultures are 

 poor, and grow very slowly. 



Relation to sunlight and dessication. An exposure of 2 hours to direct 

 sunlight CLat. -|2) kills the bacillus exposed in agar dish cultures. It suc- 

 cumbs to dessication in 6 days. 



Action of disinfectants. The disinfecting power of the following chemicals 

 was : 



Corrosive sublimate, i per cent 10-15 seconds. 



Lysol. 2 per cent 1V2-2 minutes. 



Carbolic acid, 5 per cent 12-15 seconds. 



Creolin and glycerine, equal part. 5 c.c. in 100 c.c. water 



( Friedberger-Froehncr ) 1-2 minutes. 



Lime water (Sat. solution) 10-15 minutes. 



Virulence. 



The virulence of the roup bacillus was at first weak, but was much increased 

 by passing once or twice through pigeons. Like B. pyocyoneus, the roup 

 bacillus produced suppuration, but the efifect was strictly local. 



Pathogenesis. Rabbits die after an intraperitoneal inoculation of I c.c. 



