562 



PATHOGENIC MICROORGANISMS 



Loeffler in the lesion before a diagnosis of "diphtheria" can properly 

 be made. 



Morphology and Staining. While Bacillus diphtherias presents 

 certain characteristic appearances which facilitate its recognition, it is, 

 at the same time, subject to a number of morphological variations with 

 all of which it is important to be familiar. These variations are, to a 

 limited extent, dependent upon the age of the culture and upon the 

 constitution of the medium on which it has been grown. These factors, 

 however, do not control the appearance of the organism with any degree 

 of regularity, and any or all of its various forms may occur in one and 



* *"Cr\*3&N*V " *v,v-., ^ <"^: r - ^ ^-A^.,;- v 



FIG. 59. BACILLUS DIPHTHERIA. 



the same culture. It is likely that these different appearances represent 

 stages in the growth and degeneration of the individual bacilli, but there 

 does not seem to be any just reason for believing that, as several observ- 

 ers have stated, there is definite correlation between its microscopic 

 form and its biological characteristics, such as virulence, toxicity, etc. 



The bacilli are slender, straight, or slightly curved rods. In length 

 they vary from 1.2 micra to 6.4 micra, in breadth from 0.3 to 1.1. As 

 seen most frequently when taken from the throat they are about 4 to 

 5 micra in length. They are rarely of uniform thickness throughout 

 their length, showing club-shaped thickening at one or both ends. 

 Occasionally they may be thickest at the center and taper toward the 

 extremities. When thickened at one end only, a slender wedge-shape 



