660 PROTEUS 



odour, is easily overlooked. Sometimes indefinite primary colonies are seen, of 

 variable diameter, having a smooth or slightly ringed draughtsman-like surface 

 and an entire edge. The whole growth is translucent, of the same colour as the 

 medium, butyrous, and easily emulsifiable. The complete layer of growi,h over 

 the whole plate is due to swarming of the baciUi (see text). Non-flagellated forms 

 give rise to compact colonies. 



Agar Slope. — If the organisms are inoculated into the condensation water, they swarm 

 rapidly, and in about 8 hours at 37° C. form a uniform, sUghtly raised, translucent 

 growth with a glistening, faintly contoured surface over the whole slope There 

 is a thick turbid growth in the water of condensation itself. 



Gelatin Stab. — 24 hours, 22° C. Good fihform growth, consisting of discrete and confluent 

 colonies, extending to the bottom of the tube ; smooth raised surface growth 2 or 

 3 mm. in diameter. Crateriform liquefaction is generally visible after 24 hours 

 in newly isolated strains ; liquefaction later becomes stratiform and is complete 

 in 2 to 4 days. With old laboratory strains liquefaction is slower and may not 

 be complete for 3 weeks ; sometimes the power to liquefy gelatin is lost altogether. 

 Occasionally very fine tangled branches grow out from the filiform stab. Some- 

 times the liquefaction is infundibuliform or saccate. 



Broth. — 24 hours, 37° C. Moderate growth with a sUght to moderate uniform turbidity, 

 and a moderate powdery deposit, disintegrating completely on shaking. No 

 surface growth. The growth increases only sMghtly on further incubation. 



Glucose Agar Shake. — 24 hours, 37° C. Profuse growth of tiny colonies throughout medium, 

 and layer of growth over whole surface. Numerous bubbles of gas throughout 

 medium, sometimes blowing the agar uji to the plug. 



Horse Blood Agar Plates. — 24 hours, 37° C. Uniform growth over whole surface with 

 indefinite single colonies. The blood is cleared, translucent, and of a slightly 

 brownish colour. /3-hsemolysis on 5 per cent, rabbit blood agar plates. 



MacConlcey Plates. — 24 hours, 37° C. Good growth of colourless, discrete or partly con- 

 fluent colonies. The colonies may be smooth, but more often have a slightly 

 roughish surface with an irregularly crenated, radially striated edge. 



Loeffler^s Serum. — Spreading growth over whole surface. On further incubation the 

 serum is liquefied partly or completely, but this power of liquefaction is confined 

 chiefly to maltose-negative strains. Newly isolated strains are more active hquefiers 

 than old laboratory strains. 



Dorset Egg. — 24 hours, 37° C. Spreading growth over whole surface. On further incuba- 

 tion digestion occurs, but does not usually proceed to completion. 



Cooked Meat Medium. — 5 days, 37° C. Good growth with some bubbles of gas. No 

 blackening or visible digestion occurs. 



Potato. — 5 days, 37° C. Raised, confluent, glistening, greyish-browTi growth. The potato 

 itself takes on a cafe-au-lait colour. 



Resistance. — Not specially resistant. Killed by moist heat at 55° C. in 1 hour. 



Metabolism. — Aerobe and facultative anaerobe. Growth under anaerobic conditions is 

 poor ; only a very thin, effuse, barely \asible growth is formed on agar in 4 days 

 at 37° C. No digestion of protein media occurs imder anaerobic conditions. Opti- 

 mum temperature for growth 34°-37° C. Good growth occurs at 20° C. A haemo- 

 lysin is formed, acting on rabbit blood. No pigment formed, except the cafe-au-lait 

 pigment on potato. Growth is improved by the addition of glucose and of nitrates. 

 No soluble toxin. formed. 



Biochemical. — All strains produce acid and gas in glucose, galactose, glycerol, and sucrose. 

 Nearly all strains ferment salicin, and some ferment maltose. Lactose, mannitol, 

 and mannose are never attacked. Old laboratory strains may lose their power 

 of fermenting sucrose. Litmus milk. Alkaline ; some strains coagulate the casein 



