100 MORPHOLOGIC VARIATION 



dextrose agar, the cells are arranged in short chains; later these 

 break up and the cells are singly distributed or clumped in the 

 parallel formation characteristic of diphtheria bacilli. It is non-motile. 

 With Gram's stain the reaction varies with the age of the culture. In 

 relatively young cultures, under forty-eight hours, the organism is 

 Gram-positive, but like the diphtheria bacillus not strongly so, being 

 readily decolorized if the action of the alcohol is somewhat pro- 

 longed. 



The granules within the cells give all the microchemical reactions 

 of volutin; they disappear after treatment with boiling water, they 

 stain vitally with weak solutions of methylene blue and of neutral 

 red, they retain methylene blue after treatment with 1 per cent 

 sulphuric acid, Bismarck brown, and Gram's iodine, and they stain 

 violet or reddish with old" solutions of methylene blue and with 

 toluidine blue. They vary in size, number, shape, and position 

 within the cell with the age of the culture and the nature of the 

 medium. In agar slant cultures the granules are very small, but 

 because of their intense staining quite distinct. In a twenty-four-hour 

 culture the majority of the cells contain two granules, situated near 

 the extremities of the cell ; but some cells may contain a considerable 

 number scattered throughout. During the period of active growth, 

 however, the granules decrease in number, and after six hours on 

 agar most of the cells have no granules, and those that do seldom 

 have more than one, which is centrally located. In the involution 

 forms which appear in the old agar cultures the metachromatic ma- 

 terial is variously disposed, sometimes in large irregular masses, 

 frequently as a long, narrow, twisted filament in the middle of the 

 cell. In liquid media the granules appear much as on agar, save that 

 the variations occur much more slowly. On Loeffler's blood serum 

 the granules are very large, sometimes bulging the cell, and round. 

 When the granules are quite large, as on this medium, they appear 

 to stain more intensely at the periphery. 



In media containing dextrose the granules more frequently oc- 

 cupy a position in the middle of the cell, and apparently divide 

 preceding cell division. This was most marked in a "synthetic" 

 medium composed of ammonium sulfate, dibasic potassium phos- 

 phate, magnesium sulphate, and dextrose. Here the cells were for 



