362 SUMMARY OF CURRENT RESEARCHES RELATING TO 



through their milk. Also he finds that Micrococcus melitensis may pass 

 through the placenta, and so be transmitted from the mother to the 

 foetus. Hence the once expressed hope that Mediterranean fever might 

 be eradicated by replacing infected animals (goats) by their immunised 

 offsprings would seem to have little validity, inasmuch as the offspring 

 must have M. melitensis in their blood. 



Quantitative Estimation of Soil Bacteria.* — J. G. Lipman and 

 P. E. Brown have carried out a large number of estimations, using a 

 synthetic agar medium of a slightly acid reaction, containing 1 p.c. of 

 dextrose, 2 p.c. of agar, and small quantities of potassium-hydrogen phos- 

 phate, magnesium sulphate, and potassium nitrate. It was found, in the 

 first place, that this medium allowed the development of a vastly greater 

 number of soil organisms than slightly alkaline bouillon agar. Neutral- 

 isation of the acidity of the medium caused a large reduction in the 

 number of colonies. Loam and shale soils were investigated, and the 

 effect of modifying the nitrogenous portion of the medium was tried. 

 When peptone was used as a source of nitrogen, partial neutralisation 

 reduced the number of colonies from the shale to a much greater extent 

 than those from the loam. The effects of increased acidity and increased 

 proportions of peptone were investigated, and found to vary with the 

 nature of the soil examined. 



Media for Enumeration of Bacteria in Soil.f — Hugo Fischer com- 

 pares the results of estimations of bacteria obtained by plating out soil 

 on a number of different media. The author had, previous to this in- 

 vestigation, made use of a synthetic medium suggested by Arthur Meyer, 

 which contains 1£ p.c. of agar and small quantities of mineral salts. 

 On comparing the counts obtained on this medium with those on Lohnis' 

 soil-extract medium — -containing agar, watery extract of soil and a small 

 quantity of potassium-hydrogen phosphate — he found that much higher 

 figures were obtained by using the latter medium. By using a dilute 

 (O'l p.c.) soda solution for preparing the soil extract he obtained a 

 medium on which still hio-her bacterial counts could be obtained. The 



o 



number of moulds was not affected to any great extent by the change 

 of medium. 



Stability of the Physiological Properties of Coliform Organisms.^ 

 In order to ascertain the extent to which the physiological properties of 

 these organisms depend upon the nature of their habitat, C. Kevis 

 inoculated a number of strains into sterilised earth, peat, non-albuminous 

 media, and so on. Tubes of material so inoculated were usually kept in 

 the dark, at a temperature of 20°C, for several months, and an examina- 

 tion of their fermentation reactions, vegetative characters, and so on, 

 was made each month. In general, it was found that the degree of fer- 

 mentation of sugars and alcohols was altered, and organisms which had 

 been kept on non-albuminous media lost their powers of fermentation to 

 a large extent. The type of colony was in many cases considerably 

 modified : on some highly nitrogenous soil B. coli developed a cementing 

 substance and grew into very large jelly-like colonies. In another series 



* Centralbl. Bakt., 2te Abt., xxv. (1909) pp. 447-54. 



f Tom. cit., pp. 457-9. % Op. cit., xxvi. (1910) pp. 161-78. 



