PATHOGENIC BACTERIA. Ill 



colored than the centre, and usually the bacillus stains in seg- 

 ments, so that it seems to be made up of very short sections. 

 At first sight it appears like a chain of cocci. 



Properties. They do not possess any movement; do not 

 liquefy gelatine. They are not very resistant, being destroyed 

 by a temperature of 50 C., but they have lived on blood-serum 

 five months. 



Growth. Grow readily on all media, but best on blood-serum 

 mixtures, between temperatures of 20 and 40 C. They are fac- 

 ultative anaerobic ; they grow quite rapidly and profusely. Egg 

 cultures (Hueppe's method) give good growths. Passing cur- 

 rents of air increase the growth. 



Colonies on Gelatine Plates. At 24 C. little round colonies, 

 white under low-power, granular centre ; irregular borders. 



Stab Cultures. Small, white drops along the needle track. In 

 glycerine-agar a somewhat profuse growth. 



Potato. On alkaline surface, a grayish layer in 48 hours. 



Blood- Serum (after Loffler). Blood serum 3 parts, and bouil- 

 lon 1 part ; the bouillon contains peptone, 1 per cent., chloride 

 of sodium, $ per cent., and dextrin (or glucose), 1 per cent. 



In a few hours (eight to sixteen) on the white opaque surface 

 a slight moisture is noticeable, which, if examined, is composed 

 of bacilli. In twenty -four hours small round colonies are found 

 which seem to arrange themselves concentrically. The growth 

 becomes more abundant, and the individual colonies larger and 

 yellowish. On blood-coagulum the growth is usually gray and 

 the margins of the culture crenated. Often a diagnosis can be 

 made in four hours if the serum tubes are kept in a brood oven. 



Serum- A gar. Joos finds serum-agar better than Loffler's 

 serum : 300 c.c. blood-serum mixed with 50 c.c. normal soda 

 solution and 150 c.c. water, heated in water bath for 2 to 3 hours 

 at 60 to 70 C., then raised to 100 C., or in steam chest hour. 

 Then 500 c.c. peptone bouillon (slightly alkaline) and 20 gm. 

 agar. When the agar is dissolved by heat, avoiding prolonged 

 boiling, the mixture is filtered and sterilized \ hour at 100 to 

 1W C. in autoclave ; then poured into petri dishes. Strepto- 

 cocci do not grow on this medium, whereas diphtheria bacilli 

 will grow in from 6 to 12 hours. 



