ZOOLOGY AND BOTANY, MICROSCOPY, ETC. G21 



B and thiochromogen in aqueous solution and used successively for 

 staining bacteria. 



Production of Acetic Acid in Milk by Lactic Acid Bacteria.* — Herr 

 Chr. Barthel made experiments to ascertain the quantity of acetic acid 

 produced in one and the same milk by the same species of bacterium, 

 but under different external conditions. The bacterium used was ob- 

 tained from spontaneously coagulated milk, and from its morphological 

 and biological aspect was identified as Bad. lactis acidi. The first 

 problem attacked was the difference between the amount of acetic acid 

 produced (1) in the presence of a copious supply of air, and (2) in the 

 total absence of air. The relation was found to be as 3 to 2, a con- 

 siderable difference. The second problem was to ascertain whether dif- 

 ferent temperatures exert any influence on the formation of acetic acid 

 by lactic acid bacteria. The experiments showed that the amount of 

 acetic acid produced decreased with the increase of temperature, the 

 differences in the amount however being slight. 



The inference from the foregoing facts is, that acetic acid is to a 

 certain extent a pathological product of the cell-life of the lactic acid 

 bacteria. 



Oxalic Acid Formation by Bacteria.f — Herr W. Zopf makes a pre- 

 liminary communication on the formation of oxalic acid from grape-sugars 

 by the following bacteria, — B. aceti Hansen ; acetogenum Henneberg ; 

 acetosum Henneberg ; ascendens Henneberg ; kiitzingianum Hansen ; pas- 

 teurianum Hansen ; xylinum J. Brown. All of these were found capable 

 of oxidising grape-sugar into oxalic acid. The nutrient medium used 

 contained gelatin 10 p.c, grape sugar 2-3 p.c, pepton 1 p.c, extract of 

 meat 1 p.c. The oxalic acid was deposited in the substratum in the 

 form of minute crystals of calcium oxalate. Control experiments with 

 sugar-free media gave negative results, so that the possibility of the 

 formation of oxalic acid from the carbon compounds of meat extract 

 used for making the nutrient substratum appears to be excluded. 



Inoculation of Beans with the Nodule Bacteria of Peas.J — Herren 

 F. Nobbe and L. Hiltner record a series of experiments made with root- 

 bacteria of peas and beans. They found that each plant, if inoculated 

 with the bacterium of the other, produced root-nodules, but that these are 

 usually incapable of assimilating nitrogen and of promoting growth. 

 The nodules caused by pea-bacteria on bean roots produce a vaccine- 

 material, which not only leads to nodule formation on bean rootlets, but 

 is approximately as effective ; the dried substance of beans inoculated 

 with these '* cross" bacteria amounting to 80*74 per cent., and the nitro- 

 genous to 74*8 per cent, of the quantity produced by pure bean- 

 bacteria. On the other hand pea-bacteria, according as they become 

 more and more acclimatised to the bean, become alienated in the same 

 proportion from their original host-plant. Their infectivity to the pea 

 becomes diminished ; the dried substance of peas formed by the action 

 of cross bacteria being only 69*83 per cent., and the nitrogen 49*26 per 

 cent, of the plants inoculated with pure pea-bacteria. The experiments 



* Centralbl. Bakt. u. Par., 2" Abt., vi. (1900) pp. 417-20. 

 t Ber. Deutsch. Bot. Ges., xviii. (1900) pp. 32-4 (2 figs.). 

 X Centralbl. Bakt. u. Par., 2 ,e Abt., vi. (1900) pp. 449-57 (1 pi.). 



