90 SUMMARY OF CUEIJENT liESEARCHES RELATING TO 



for by means of metaphenylene-diamine-hydrochloride and sulphuric 

 acid. The formation of ammonia was demonstrated by means of 

 Nessler's test. The experiments showed that the denitrifying power of 

 bacteria in American tropical seas is considerably greater than that 

 of bacteria in water at the north of the Bay of Biscay. The former 

 have the power of breaking down nitrates completely, a property which 

 bacteria in the temperate seas do not possess. 



The author has also shown that these bacteria can precipitate calcium 

 carbonate from solutions of simple calcium salts, and suggests that such 

 action may, in the past, have played an important part in the precipita- 

 tion of various rocks, such as chalks and limestones. 



Common Bacteria in Laboratory Tanks.* — G. H. Drew gives in 

 tabular form a rough classification of eight of the most common species 

 of bacteria found in the Laboratory Tanks at Plymouth. Only the 

 forms which occur free in the water have been considered. The media 

 employed were similar to those used in ordinary bacterial work, except 

 that fish broth was used in place of meat broth, and sea-water instead of 

 tap-water. The table shows the morphological and cultural characters 

 of these organisms, which, pending more detailed study, are designated 

 by numbers instead of names. It appears, however, that one of the 

 organisms described may be identified as Bacillus repens of Grau. 



Bacterial Flora of River Water .f — In samples of water taken from 

 the river Main above Wiirzburg, A. Reiss found 44 different types of 

 organism, including certain varieties of Bacillus 2)roteus, and a number 

 of intestinal forms. These were probably derived from the drainings of 

 cultivated land and towns nearer the source of the stream. In samples 

 collected below the town of Wiirzburg, 18 additional species were found. 

 These included organisms resembling, culturally and morphologically, 

 some of the pathogenic forms such as Streptococcus pyogenes, Bacillus 

 septicsemiae hsemon-Juigicse, and B. murisepticum. It was found, how- 

 ever, that such organisms had lost their pathogenicity, but the author, 

 adducing the diminution in virulence observed in laboratory strains of 

 bacteria under certain conditions, considered that the bacteria recovered 

 from the river samples were identical with the pathogenic types. Quan- 

 titative observations upon the relative frequency of various organisms 

 were carried out, and are set forth in tables. 



Variations in Proteus Group.J— T. H. Glenn has made a study of 

 some variations in the fermentation properties of some members of this 

 group. Working with Proteus vulgaris, he was unable, by selection, to 

 produce any variation in its acid-producing properties. It was found 

 that this orgauism would ferment lactose under anaerobic conditions, 

 but not otherwise. Fermentation products of carbohydrates inhibit the 

 production of indol. The addition of more than • 5 p.c. of lactic acid 

 has the sarue effect. The ferment produced by P. vulgaris appears to 

 be a tryptic, that of Bacillus cloacse a peptic ferment. Proteus zopfii 



* Journ. Marine Biol. Assoc, xi. (1911) pp. 161-3. 



t Verb. Phys. Med. Gesell. Wiirzburg, xli. (1911) pp. 107-50. 



X Centralbl. Bakt., Ite Abt, Orig., Iviii. (1911) pp. 481-95. 



