— 163 — 
Journal of Hygiene, Nov. 1908, p. 609-G/i 5) Atlenlion is called to the role 
of the nitrifying bacteria, the nitriie hacleria converting ammonia into nitrite, 
and tlie nitrale bacteria carrying the oxidation a stage further with formation 
of nitrate. 
When these organisms are grown on ordinary laboratory media, minute 
quantities of organic material inhibit their growth (especially the nitrite 
forms), while ammonia, present in appreciable quantity, inhibits tlie nitrate 
bacteria. Winogradsy, following Omeliansky, has, however, shown that in 
nature the growth and activity of the nitrite-forming bacteria are not inter- 
fered with by the presence of organic material. As regards difficulty of for- 
mation of nitrate in presence of ammonia, experiments by Boullanger and 
MassoU'^) indicate that ammonia has a much greater power of inhibiting the 
growth of the nitrate-forming bacteria than of interfering with their activity 
when growth has been once established. 
ff. All these results deal with surface conditions, and give us no idea of the 
reactions taking place in deep-sea deposits, where organisms are constantly 
perishing and being buried beneath accumulations of detrital or organic origin. 
In this connection an article by the late George Harold Drew in Publication 
n° 182 of the Carnegie Institution of Washington, 19 lû, p. 1-78, is worthy 
of careful consideration. The following points were raised : 
1. In the seas of the American tropics, bacteria exist which actively preci- 
pitate calcium carbonate from the calcium salts present in solution in sea- 
water. 
2. The destruction of nitrates by bacterial action in the seas of the Ame- 
rican tropics is far in excess of that occurring in temperate climes. 
3. Attention is directed to the fact that no accurate method of determining 
the nitrate contents of sea-water at present exist. 
à. The existence of nitrifying bacteria, which are capable of absorbing and 
combining with the free nitrogen of the air, eventually giving rise to nitrates, 
has been shown by Keding, Wiss. Meeresunters , vol. IX, Kiel, 1906, and by 
Kenter, Wiss. Meeresunters, vol. VIII, Kiel, but these have so far only been 
I am particularly indebted to Mr. A. Lucas, Director of the Government Analytical Labo- 
ratory, for much valuable help in regard to literature, etc. concerning these questions. 
Ann. Inst. Pasteui; XVII, p. /jgg, and XVIII, p. 181. 
2 1 . 
