1923] 



JENNISON — POTATO BLACKLEG 43 



and detailed to enable one to identify the disease ascribed to the 

 bacterium named and described as the cause. 



For a number of reasons Smith ('20) believes it best to retain 

 AppeFs name, especially as van Hall made very few inoculations 

 under natural conditions, and further, because he says of his 

 organism: "On artificial media the parasite loses its virulence 

 very quickly." This contention loses weight in the light of a 

 similar statement made by Smith on a preceding page (see 

 Smith, '20, page 263), as follows: "It is common belief (of Ger- 

 man origin) [italics not in original] that the organism loses 

 virulence readily." The writer feels that Smith's further objec- 

 tions to the use of van Hall's name are largely refuted by the 

 data and facts previously presented. 



It was inevitable that questions involving nomenclature should 

 have appeared in this paper and a serious attempt has been made 

 to give all names most careful consideration. On the grounds of 

 priority as well as for other reasons brought out above the writer 

 believes that Bacillus atrosepticus 1 van Hall should stand. 



REVISED DESCRIPTION OF BACILLUS ATROSEPTICUS VAN HALL 



Index No. 5312-32120-2111. 2 



Microscopic features.— The potato blackleg bacillus is a small 

 non-sporiferous, Gram-negative rod, having an average diam- 

 eter of about 0.6 ji and a length (1.5 m) slightly exceeding twice 

 its diameter. The organism is actively motile by means of a 

 few peritrichic flagella. No capsule is demonstrable by the ordi- 

 nary methods now in use. 



Physiological characteristics and cultural features.— -The or- 

 ganism is non-chromogenic in agar, gelatin, nutrient broth, and 

 other common media. On agar slants growth is moderately 

 abundant. The surface is smooth and the luster is glistening. 

 Agar colonies are small, round to somewhat irregular in form, 

 and, under a magnification of 50 diameters, they appear to be 

 granular in structure. 



Gelatin is liquefied, the action being visible on the second day, 

 if not before. Colonies on gelatin plates are white, round, and 

 noticeably larger than those which develop on agar. 



'According to a recently suggested outline of bacterial classification (Winslow 

 et al, 20) the name would become Erwinia atrosepticus nov. comb. 



'See Descriptire Chart indorsed by Soc. of Am. Bacteriologists, Dec. 30, 1920. 



