224 SUMMARY OF CURRENT RESEARCHES RELATING TO 



and in tho protoplasmic bands. The cell-wall is composed of two 

 layers differing from one another in their property of swelling. The 

 only mode of multiplication is by intercalary division. 



Decomposition of Nitrates and Nitrites by Bacteria.*— A. Maassen 

 found that potassium nitrate in 0'5 p.c. solutions containing 5 p.c, 

 pepton was reduced to nitrite by 85 of the 109 varieties of microbes 

 examined ; 50 destroyed nitrites and 4 liberated free nitrogen. Many 

 bacteria which reduced nitrites without liberation of oxygen, had little 

 or no effect on nitrates. The presence of carbohydrates is favourable 

 to denitriiication, whilst, in absence of organic nitrogen, nitrates and 

 nitrites are attacked by microbes which have no effect when proteids are 

 present. The so-called denitrifying organisms destroy nitrates inde- 

 pendently of the nature of the nutritive solutions, whilst others act 

 only in presence of certain carbon compounds. The action of both 

 classes of microbes is retarded by the presence of highly oxygenated 

 compounds, such as chlorates, without injury to their growth. Some 

 bacteria, such as Bacterium prsepollens, act on nitrates only in symbiosis 

 with other varieties, liberating nitrogen, and producing potassium car- 

 bonate. The co-operating bacteria in the case of B. prsepollens are 

 exclusively those which reduce nitrates to. nitrites. 



Chlamydospores of Bacteria. | — Prof. A. Meyer expresses the 

 opinion that many species of the genus Bacillus are capable of forming 

 chlamydospores. In old cultures of Bacillus coheereus, ellenbachensis, 

 and ruminatus can be found forms which are extremely like the chlamydo- 

 spores of fungi. Such forms are cells rich in plasma, often vacuolated, 

 and always invested in a thick membrane, and stain well with fucksin, 

 or with iodopotassic iodide. In connection with this question, it is men- 

 tioned that the cell-membranes of some bacteria stain blue with iodine : 

 thus Bacterium pasteurianum and Mtzingianum Hansen both do in 

 mass, as Hansen showed, while the author finds that it is the internal 

 lamina of the membrane which becomes blue when the cell is treated 

 with iodopotassic iodide, which renders it probable that the bacterial 

 mucus is formed by the swelling up of the outer lamina of the mem- 

 brane. 



Effect of the Human Gastric Juice on Cholera Vibrios. J — Dr. 

 Schultz-Schultzenstein obtained the following results. _ When the cholera 

 vibrio is suspended in pure water it is killed in 6 minutes by the addi- 

 tion of • 05 p.c. of acid. Pepsin plus a trace of acid acts inhibitively on 

 the vibrios and causes them to become granular. The association^ of 

 pepsin and hydrochloric acid is fatal to the vibrios when the proportion 

 of acid reaches 0-019 p.c. 600 c cm. of water removed, after a stay of 

 12-15 minutes, from the stomach, was found in 75 p.c. ( f the cases to 

 have acquired an acidity of 0-03 p.c, and such water was able to kill 

 cholera vibrios in 15 minutes. In 25 p.c. of the cases the quantity of 

 the acid was less, and when it did not amount to more than 0*0142 p.c. 

 the vibrios were not killed in 1£ hours. 



In fluids containing albumen or pepton, or both, a much greater 



• Arb. k. Ges.-A., xviii. (1901) pp. 21-77. See Journ. Chem. Soc, Abst. ii., lxxxii. 

 (1902) p 39. t Ber. Deutscli. Bot. Ges., xix. (1901) pp. 423-31 (1 pi.). 



X Centralbl. Bakt., 1" Abt., xxx. (1901) pp. 785-90. 



