336 



Suppuration 



Under certain conditions the wandering of tlie processes can b^ directly observed 

 under the microscope. It depends not only upon the culture-medium, but, in 

 part, upon the culture itself. Entire groups of bacilli or single threads, by 

 gradual extension and circular movement, detach themselves from the colony and 

 wander about upon the plate. From the radiated central part of the colony 

 peculiar zooglea are formed, having a sausage or screw shape, or wound in spirals 

 like a corkscrew. The younger colonies, which have not yet reached the surface 

 of the gelatin, are more compact, rounded or nodular, later covered with hair-like 

 projections, and becomiilg radiated like the superficial colonies." 



If the culture-medium be concentrated, or the culture have been 

 frequently transplanted, the phenomenon is less marked or may not 

 occur. 



Bouillon. — ^In this medium the organism grows rapidly, and - 

 quickly clouds the fluid. A pellicle soon forms upon the surface and 

 a mucilaginous sediment occurs later. 



/ 



Fig. 113.- 



-Swarming islands of proteus bacilli on the surface of gelatin; X 650 

 (Hauser). 



Gelatin Punctures.- — Puncture cultures in gelatin are not char- 

 acteristic. A stocking-like liquefaction occurs and extends so rap- 

 idly that the entire medium is liquefied in a few days. Anaerobic 

 cultures do not liquefy. 



Agar-agar. — Upon agar-agar the bacillus forms a moist, thjn, 

 transparent rapidly extending layer which rarely reaches the sides 

 of the tube. Upon agar-agar plates ameboid movement of the 

 colonies sometimes occurs. 



Potato. — Upon potato the growth occurs in the form of a smeary 

 patch of soiled appearance. 



Milk is coagulated and peptonized. 



Metabolic Products. — ^The bacillus rapidly decomposes pro- 

 teins, albumen, fibrin, blood-serum and gelatin. According to 



