252 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Referring to the use of paraffin in excluding oxygen, the author 

 demonstrated by several experiments, employing light bacteria, that 

 paraffin is useless, since it not only allows the passage of oxygen, but can 

 store it up. 



The author concludes from his observations, that both obligate and 

 falcultative anaerobes can live for a number of generations, without any 

 functional alteration, in complete exclusion from free oxygen. The 

 similar behaviour of these two classes of organisms expresses the fact 

 that potential anaerobes are just as good representatives of anaerobic life 

 as the essential anaerobes, over which they have the advantage of bein<„ r 

 able to grow normally also in air. 



Isolating the Nodule Organism of the Leguminosse.* — F. C. 

 Harrison and B. Barlow have examined upwards of thirty species of 

 Papilionaceas, and with two exceptions, found nodules developed on the 

 roots. To isolate the nodule organism the authors employed a medium 

 consisting of wood ashes, which contains phosphate, sulphide and 

 chloride of potassium, sodium, calcium, magnesium and iron, but no 

 nitrogen, to which was added some form of sugar. Fresh ashes were 

 shaken up in water, boiled and filtered, and to various strengths of the 

 aqueous filtrate 2 to 5 p.c. of maltose were added. Ash maltose agar 

 was also used. 



To isolate the Pseudomonas radicicola, the root of the plant is washed 

 under a tap, and a nodule is removed with forceps and immersed in an 

 aqueous solution of hydrochloric acid and mercuric chloride crystals for 

 two to three minutes ; it is then placed on a filLer-paper moistened with 

 the same solution, and cut open by a specially made knife needle, 

 previously flamed, and portions of bacteroidal tissue are removed into 

 sterile water in a Petri dish. From the resulting emulsion cover-slips 

 were prepared and stained, and ash agar plate cultivations were made 

 and incubated at 20° C. No other organisms were detected in the 

 nodules besides the Pseudomonas radicicola. On ash maltose agar, in 

 two to three days it forms a raised, transparent, wet, shining, spreading 

 growth, which draws out into a fine thread when touched with a needle. 

 Cultures on this medium remain alive for over a year. The organisms 

 are small rods, often swollen at one end, and rarely branched ; they are 

 actively motile, and a single polar flagellum may be developed ; the cell- 

 contents are not uniform, often concentrated in bands, and varying with 

 the species of the legume, the condition of infection and growth, the age 

 and size of the nodule, and the portion of the nodule examined. They 

 stain well with ordinary dyes, but are decolorised by Gram's method. 

 The authors give some reports showing the benefit obtained by the 

 distribution of pure cultures of Pseudomonas radicicola in Canada. 



Method for Isolating Anaerobes.f — F.Marino describes the following 

 simple method for isolating anaerobic bacteria. ; > >0-:'>. r > c.cm. of a mixture 

 of ordinary agar and 3-5 p.c. glucose are distributed into large test- 

 tubes. When required for use such a tube is melted, and on attaining 

 a temperature of 42°, 1 c.cm. of rabbit or horse serum is passed in ; the 



* Centralis. Bakt., 2te Abt. xix. (1907) p. 264. 



t Ann. Inst. Pasteur, xxi. (1907) pp. 1005-8 (2 figs.). 



