92 SUMMARY OF CURRENT RESEARCHES RELATING TO 



artificial media. These two types do not otherwise differ, and both 

 produce plague in rodents. The author has shown that type (2) has 

 been derived from type (1) by a series of passages through the rat, and 

 that this attenuated variety of Bacillus pestis can be experimentally 

 produced, and will breed true. 



Direct Microscopic Preparation of Cheese.* — A. Rodella has 

 applied the method devised by Gorini of making stained preparations of 

 fresh and also alcohol-hardened sections of cheese in various states of 

 ripeness, and which can be compared with the results of cultural 

 experiments, to the examination of Emmenthal and Gorgonzola cheeses. 

 The author also makes impression preparations by pressing small por- 

 tions of cheese between two slightly warmed slides on which impressions 

 of the cheese are left, and after removing the fat by chloroform and 

 alcohol, can be stained and compared with the section preparations. 

 He finds that bacteria are collected in colonies of varying sizes, which 

 are distributed irregularly throughout the cheese ; occasionally these 

 bacterial collections include several varieties of organisms ; that the 

 intervals between the collections is usually not quite free from micro- 

 organisms. 



Two New Pigment-producing Bacteria, t — 8. v. Bazarewski de- 

 scribes a bacillus and a coccus that produce pigment. Bacillus brunneus 

 rigensis, isolated from soil, is an oval motile rod 1 • 7/J.-2 ' 5 fx. long by 

 0"75/tt broad, with long flagella ; it stains by the ordinary dyes but not 

 by Gram's method ; spore production was not observed ; in old cultures 

 capsules are formed ; brown granular colonies are formed on gelatin, 

 which is completely liquefied within a week ; the growth on agar is white, 

 the condensation water is clouded and has a brown deposit, and in old 

 cultures the whole mass of the agar assumes a brown colour ; broth is 

 clouded after two days at room temperature, showing a brown pellicle 

 and later a brown deposit, the medium remaining alkaline ; on potato 

 there is a yellow growth, which later together with the potato takes a 

 dark brown colour ; milk remains unchanged ; there is no production 

 of gas or indol ; it is a potential anaerobe ; optimum temperature 30° C. ; 

 it is not pathogenic for white mice ; the brown colour is soluble in water 

 and alcohol, but insoluble in ether, and unchanged by concentrated 

 nitric acid. 



Micrococcus citreus rigensis, isolated from the air of the laboratory, 

 as round isolated cells 1 • 2-fi-l ' 5 /a diameter ; stains by ordinary dyes, but 

 not by Gram's method ; forms slow-growing sulphur-yellow colonies on 

 gelatin, which commence to liquefy after 10-14 days ; on agar it forms 

 a sulphur-yellow growth, the condensation water remaining clear with a 

 yellow deposit ; on potato there is formed a slimy growth of a deeper 

 yellow than the growth on gelatin, and the potato itself remains un- 

 changed ; milk remains unchanged ; there was no production of acid, 

 gas or indol ; it is a firm aerobe ; optimum temperature 30° C. ; it is 

 pathogenic for white mice. The yellow pigment is insoluble in water, 

 alcohol, ether, chloroform, and benzine. 



* Centralbl. Bakt., 2te Abt., xv. (1905) p. 143. 

 t Tom cit., p. 1. 



