ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 551 



well upon glucose or maltose agar, forming colonies at first yellow, later 

 white, not markedly raised aboye the surface of the medium. It 

 differs thus from the species T. crateriforme, T. accuviinatwn, and 

 T. violaceum in the form and the colour of its colonies. The author 

 proposes, in a future communication, to supplement this preliminary 

 note with a description of the life-history of the organism. 



Spirochaetes of the Mouth.* — G. Repaci has made a study of certain 

 types of spirochaete isolated from dental tartar or from diseased areas of 

 buccal mucous membrane. He describes briefly his methods. In order 

 to get pure cultures of these organisms, the tartar was broken up finely 

 and washed at 37° C. to remoye coarser portions of tartar. The surface 

 of- the fluid, containing free-swimming spirochaetes, is used for culture. 

 Cultivations were made after the method of Veillon, under strict an- 

 aerobic conditions. F'our species. A, B, C, D, were isolated, and their 

 cultural and morphological characters are discussed. The forms A and 

 C appear to be intermediate between Spirillum huccalis and S. dentium ; 

 the form D differs from S. crassum only in that it is longer and is 

 devoid of cilia. 



Bacterial Activities in Frozen Soils.! — P. E. Brown and R. E. 

 Smith have investigated the bacterial content of soil when the tem- 

 perature is below 0° C, and find that increases and decreases in the 

 number of organisms occur in frozen soil, and that larger numl^ers are 

 present after the soil has been frozen for a considerable time than before 

 it begins to freeze. Their observations by means of the modified synthetic 

 agar plate method appear to confirm Conn's hypothesis that there is in 

 soil a special group of organisms favoured by low temperatures. Frozen 

 soils possess relatively high ammonifying power, but relatively low nitri- 

 fying power. The nitrogen-fixing power of frozen soils increases with 

 the continuance of the frozen period. While the soil is gradually 

 cooling, its denitrifying power increases until the soil becomes frozen, 

 when it diminishes again. These physiological results support the theory 

 that specific groups of hardy bacteria flourish in frozen soil. 



Acid-forming Milk Bacteria. — After a general survey of the litera- 

 ture of this subject, and a review of the chief types of organism present 

 in the various forms of soured milk used in Asia and the eastern parts 

 of Europe, A. Wolff J considers in detail certain types of lactic acid 

 producers and other ferments encountered in dairy work. The most 

 common form is the Bacterkim Jactis acidi (Leishmann), usually occurring 

 as a short rod, but at times assuming a streptococcal form. More atten- 

 tion is paid to the long forms of lactic fermentation in all their variations 

 and to the propionic acid formers, particularly with reference to the 

 part they play in the manufacture of cheese. 



New Intestinal Bacillus. — By making cultivations from the intes- 

 tinal contents upon a medium containing histidiu, A. Berthelot and 



* Ann. de I'Inst. Pasteur, xxvi. (1912) pp. 536-55. 

 t Centralbl. Bakt. 2te Abt., xxxiv. (1912) pp. 369-85. 

 X Centralbl. Bakt. 2te Abt., xxxiv. (1912) pp. 494-540. 



