ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 689 



wide marginal zone bounding the known infected area. The great 

 majority of these rats were perfectly healthy. Seventy-three rats, set 

 aside for further enquiry, either because the possibility of plague infection 

 was suspected or because some pathological feature of interest was 

 present, were found to be infected with the Gaertner bacillus or some 

 other irrelevant organism. From three rats an organism w T as isolated 

 which resembled the Bacillus pestis morphologically and culturally. 

 Further investigation, however, of the sugar reactions of these organisms 

 and of their virulence to rats showed that they must be regarded as 

 identical with B. pseudotuberculosis rodentium rather than B. pestis. 

 So that no plague-infected rats were found in the marginal zone 

 investigated. 



Bacteriological Studies of Danish Butter.* — 0. Jensen remarks 

 upon the use of lactic ferments in the preparation of butter, and states 

 that his investigations show that such soured butter remains freer from 

 contamination by harmful organisms than simple butters. Pasteurization, 

 salting, and lactic ferments are three factors which cause a simplification 

 in the flora of butter. The lactic acid organisms principally used in 

 Denmark are two species of streptococci, a finer form, Diplococcus acidi 

 lactici, and a coarser form, occurring in long chains. It has been found 

 that the two organisms working together have a greater lactic fer- 

 mentation power than have either of them when working in pure 

 culture. Discussing the disorders of butter, the author mentions 

 " cheesiness," which is due to the invasion of Streptococcus casei amari. 

 He has also found in some samples a butter-fat-splitting form, Bacillus 

 fluorescens liquefaciens. The author further discusses moulds and yeasts 

 met with upon butter under various conditions. 



Variation and Adaptation in Bacteria. f — E. W. A. Walker, who 

 has made observations upon streptococci with special reference to the 

 value of fermentation tests as applied to these organisms, arrived at the 

 following conclusions. The reactions of any given strain of strepto- 

 coccus in Gordon's mediaj vary considerably under the conditions of 

 ordinary laboratory cultivation, and by suitable manipulation of the 

 culture-media they can readily be made to vary very greatly. The 

 results obtained entirely oppose the view that these reactions afford a 

 means of distinguishing fixed and definite varieties among streptococci 

 isolated from the human subject. Such differences as are observed are 

 of a temporary and accidental character, and are not in any sense 

 specific, though they may perhaps afford some evidence of the natural 

 habitat or previous environment of the organisms concerned. 



Schroeter& Gutjahb — Vergleichende Studien der Typhus-coli-Dysenteriebak- 

 terien in Auschlass an eine kleine Ruhr, epidemie in Mitteldeutschland. 



Centralbl. Bakt., It" Abt. Orig., lviii. (1911) pp. 577-624. 



Stevenson, W. — The Distribution of the '"Long Lactic Bacteria" — Lactobacilli. 



Centralbl. Bakt., 2«* Abt., xxx. (1911) pp. 345-8. 



* Centralbl. Bakt., 2te Abt., xxix. (1911) pp. 610-16. 

 t Proc. Roy. Soc, Series B, lxxxiii. (1911) pp. 541-58. 

 X See this Journal, TJOt;, p. 87. 



