332 



BACTERIOLOGY. 



applied, and exclusively applied, to that acute infectious 

 disease usually associated with pseudomembranous affec- 

 tion of the mucous membranes which is primarily 

 caused by the bacillus diphtherise of Loffler. Other 

 bacteria do, indeed, occasionally produce lesions which 

 simulate in one way or another those caused by the 

 diphtheria bacillus, but none of them ever produce 

 lesions similar in their totality to those of a charac- 

 teristic case of diphtheria. 



Morphology. When cover-glass preparations made 

 from the cultures grown on blood-serum are examined 

 the diphtheria bacilli are found to possess the following 

 morphological characteristics : The diameter of the 

 bacilli varies from 0.2^ to 0.8/j. and the length usually 



FIG. 41. 



FIG. 42. 



One of very characteristic forms ot 

 diphtheria bacilli from blood-serum 

 cultures, showing clubbed ends and 

 irregular stain. X 1100 diameters 

 Stain, methylene-blue. 



Extremely long form of diphtheria 

 bacillus. This culture has grown on 

 artificial media for four years and 

 produces strong toxin. X 1100 diam- 

 eters. 



from I/jt to 6//, but exceptionally even longer (see 

 Fig. 42). They occur singly and in pairs (see Figs. 41 

 to 44), and very infrequently in chains of three or four. 

 At times, especially in the tissues, branching forms are 



