726 SUMMARY OF CURRENT RESEARCHES RELATING TO 



B. pyocyaneus, and obtained good growth and a formation of pigment 

 on a medium composed of asparagin 0"2 p.c, magnesium sulphate 

 0*05 p.c, potassium sulphate 0-02 p.c. The author found that an 

 addition of ' 05 p.c. of ferrous sulphate to ihis medium stopped growth 

 almost entirely, and that the addition of • 002 p.c. permitted growth, 

 but prevented pigment formation ; probably iron is necessary for 

 growth, but that which exists as an impurity of the medium is probably 

 sufficient, and may be regarded as negligible, and he concludes that the 

 above medium is sufficient. By substituting the magnesium sulphate 

 for potassium sulphate only a diminished growth was obtained, and no 

 growth occurred unless the medium was free from alkali ; when only 

 ^ mg. per 100 c.cm. is added, growth and pigment production are less 

 than when larger amounts are added, and with smaller amounts only 

 cloudiness of the medium occurs, and without production of pigment. 

 The author concludes that potassium is necessary for the growth of these 

 organisms, since similar results were obtained by substituting salts of 

 lithium, ammonium, and rhubidium for the potassium salt. In a similar 

 way the author has shown that the presence of magnesium is necessary 

 for the growth of these organisms. 



Bacillus minimus mammae.* — C. Gorini gives the cultural and 

 morphological characters of a bacterium isolated two years ago from the 

 teat of a cow made sick by bad milking. It is a very minute bacillus 

 found in milk cultuj-es in pairs, short chains, and small aggregations. 

 It is non-motile, and does not form spores. It stains with the usual 

 aniline dyes, but not by Gram's method. It grows only anaerobically. 

 The colonies are more or less rounded. Milk is coagulated with forrna- 

 tion of acid, and the production of a presamigenous (rennet) peptonising 

 ferment. 



* Rend. R. Istit. Lombardo, xl. (1907) pp. 947-52 (2 figs.). 



