no AIDS TO BACTERIOLOGY 



Buchanan (Medical Press, June 30, 1909) is of opinion 

 that water is not so often to blame as is generally imagined. 

 MacGonkey's lactose agar or Conradi-Drigalski agar 

 may conveniently be used for isolation of the bacilli 

 from faeces. On the former white colonies, and on the 

 latter small clear blue colonies, are worked up. 



CHAPTER VIII 

 THE DIPHTHERIA BACILLUS 



Morphology. The Klebs-Loffler bacillus (B. diphtherice) 

 is a delicate, slender, non-motile, and non-sporing organ- 

 ism, having rounded ends. Its length is variable, long, 

 medium, and short varieties being described, the usual 

 length seen being 3 ^ to 5 //. Both in the membrane and 

 in cultures a remarkable parallelism in arrangement is 

 seen, and club-shaped forms are frequent. 



It is not killed by drying; dust containing the bacillus 

 will retain its virulence for months under certain condi- 

 tions. The organism is aerobic and facultatively anaerobic, 

 and its thermal death-point is 58 C. 



Staining. When stained with Loffler's alkaline methy- 

 lene blue, the staining is frequently irregular, darker and 

 lighter stained portions alternating the so-called ' seg- 

 mentation ' ; sometimes the poles are deeply stained, 

 appearing as dark dots at the ends ' polar staining ' ; 

 and occasionally there is a change of tint to a pinkish 

 here and there ' metachromatism.' 



Wesbrook divides the bacillus into three types: The 

 ' solid ' type stains uniformly ; the ' barred ' form shows 

 intervening segments, which either stain but slightly or 

 not at all; and the granular type (which predominates 

 in clinically characteristic affections) has deeply staining 

 granules. The bacillus is Gram-positive, and as con- 

 firmatory stains Neisser's or Pugh's stains are generally 

 used, 



Neisser's diagnostic stain: A preparation for about 

 thirty seconds is treated with the following solution: 

 One gramme of methylene blue dissolved in 20 c.c. of 

 alcohol, and mixed with 950 c.c. of distilled water and 

 50 c.c. of glacial acetic acid. It is rinsed in water, treated 



