ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 405 



merits is a most complex subject, and it appears that in the majority of 

 cases, e.g. B. oulgaricus and Streptococcus lacticus, more satisfactory 

 results are obtained by the use of two organisms in symbiosis than with 

 pure cultures. Barillas Mlgaricus alone may have some effect upon the 

 fat of milk, producing a small quantity of a nauseous product. 



The author gives a general account of the methods in use for pre- 

 paring sour milk, and refers to its therapeutic applications. The extent 

 to which the Bulgarian bacillus has developed can be readily observed 

 by bacterioscopic methods, as the morphological characters of this 

 organism are so distinctive. In conclusion, particulars are given of the 

 comparative efficacy of a variety of preparations supplied to the author 

 for investigation. 



'.-■ 



Bacillary Disease among Fish.* — In the summer of 1910, fish of 

 tlie species Leuciscus rutilus, in the lake of Nantua, perished in large 

 numbers. The epizootic attained such proportions that not only did the 

 fishermen sustain serious loss, but it became necessary in the interests of 

 public health to collect and destroy the dead fish. The condition was 

 investigated by L. Mercier and R. de Drouin de Bouville. The diseased 

 fish came to the surface of the water, tried ineffectually to dive again, 

 struggled, lost their equilibrium, turned on one side, and remained 

 motionless until death. Lesions of the scales were found, which sug- 

 gested that the condition was one of Lepidorthosis contagiosa, due to the 

 Bacillus pestis astaci. From one of the diseased animals an organism 

 identical with this was recovered. The organism is flagellate, motile, 

 Gram-negative ; it produces a turbid growth in broth, liquefies gelatin, 

 and coagulates milk. Inoculations of small doses into crayfish caused 

 death in four days, with symptoms typical of Pestis astaci. The fish 

 disease was also reproduced artificially by inoculation. It appears, there- 

 fore, that this disease is maintained in this lake in an enzootic form by 

 the presence of these two hosts of the micro-organism. 



Nitrifying Organisms in Soil.j — H. Pringsheim gives a concise 

 general account of the micro-organisms occurring in soil, which perform 

 a nitrogen-fixing function. The first group mentioned comprises those 

 organisms which form root-nodules on leguminous plants. The sub- 

 division of these into classes affords a problem which the systematist has 

 yet to solve. It appears, however, that different varieties affect different 

 species of plants, and it has been found difficult, in some cases, artificially 

 to infect a plant with an organism associated normally with another 

 species. The organisms living free in the soil fall into two classes. 

 One type, isolated first by Winogradsky, is a sporing bacterium, of 

 a Clostridium form. Azotobacter, a rounded form, was cultivated by 

 Beijerinck in a mannite-containing medium. The author deals further 

 with the distribution of these organisms, and with problems connected 

 with their metabolism. He considers the question of the decomposition 

 of cellulose ; and refers, in conclusion, to inoculation experiments per- 

 formed with different types of nitrifying organisms. 



* Coniptes Rendus, clii. (1911) pp. 289-92. 

 t Biol. Centralbl., xxxi. (1911) pp. 65-81. 



