514 PATHOGENIC MICROORGANISMS 



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'thronl 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 

 results. Such forms are usually straight, of smaller size than their 

 neighbors, and are more often stained with great uniformity. These 

 are spoken of by Beck 1 as the "ground type," and assumed, for in- 

 sufficient reasons, to be the young individuals. Branched forms 

 have been described by some investigators. They are rare and 

 probably to be regarded as abnormal or involution forms due to un- 

 favorable environment. 



The organisms stain with the aqueous anilin dyes. A characteristic 

 irregularity of staining which is of great aid in diagnosis is best obtained 

 with Loeffler's "alkaline methylene-blue." (For preparation see section 

 on Staining, p. 96.) Stained with this solution for five to ten minutes 

 many of the bacilli appear traversed by unstained transverse bands 

 which give them a striped or beaded appearance. The longer indi-- 

 viduals often have a strong resemblance to short chains of strepto- 

 cocci. Others may appear unevenly granular. In cultures which 

 are about eighteen hours old, many of the bacilli may show deeply 

 stained oval bodies situated most frequently at the ends. These are 

 the so-called "polar" or "Babes-Ernst" bodies. 2 Special stains have 

 been devised for the demonstration of these appearances. One of these 

 was originated by Neisser, 3 who claims for it differential value in 

 distinguishing these organisms from pseudodiphtheria and xerosis 

 bacilli. 



His method requires two solutions: 



1. Methylene blue (Griibler) 1 gram. 



Alcohol, 96 per cent 20 c.c. 



Glacial acetic acid 50 " 



Water 959 " 



2. Bismarck brown 2 grams. 



Wat er 1,000 c.c. 



1 Beck, in Kolle und Wassermann, ii, p. 773. 



2 Babes, Zeit. f. Hyg., Bd. v, 1889. 

 Neisser, Zeit. f. Hyg., xxiv, 1897. 



