& 
1887.] MICROSCOPICAL JOURNAL. 149 
organisms, but upon very insufficient grounds, and actual experiment shows 
that under favorable conditions of growth their numbers actually increase. 
The results observed are as follows: 
Flours of subsidence. Number of centres per cc. 
Oo LOS 
6 6,028 
24 7,202 
48 48,100 
By the addition of lime, as in Clark’s process to make hard waters soft, the 
precipitated carbonate carries down with it the greater number of living organ- 
isms. This process may be advantageously applied on a large scale. 
Pasteur’s filter, a cylinder of biscuit porcelain through which the water is 
forced, when new, appears to separate all the organisms in the water, but it 
soon becomes clogged. 
Prof. C. J. H. Warden, Surg. H. M. Bengal Army, has described the methods 
in use at the Reich’s Gesundheits Amt, Berlin, with illustrations.* The sub- 
ject is well treated, and the concluding article has an elaborate table showing 
the results of numerous chemical and bacteriological examinations of waters, 
from various sources, which will be valuable to anyone engaged in such work. 
Dr. T. Leonef has described some investigations to determine the rapidity 
of increase of the micro-organisms in samples collected and kept for a time. 
These results are of practical interest and importance, since they clearly show 
the necessity of immediate examination. At first thought it might be sup- 
posed that the increase would depend upon the nutrient quality of each kind 
of water, and that very pure water would show very little increase of life. 
The results indicate, however, that even very pure water may support a con- 
siderable number of living organisms. For example, the Mangfall water, 
supplied to the city of Munich, leaves a residue of only 284 millegrammes 
per litre, and contains not a trace of nitrates, nitrites or ammoniacal salts, 
and scarcely any organic matter.{ This water, when drawn from a cock, 
showed five microbes in a cubic centimetre; after twenty-four hours, at 
14°-18° C., it showed more than one hundred ; in two days, 10,500; in three 
days, 67,000; in four days, 315,000; in five days, more than half a million. 
A similar increase was observed when the water was kept inmotion. These 
results fully confirm those already quoted from Frankland’s experiments. 
It should be remembered that this increase will not continue indefinitely, 
but after a certain point the number of organisms will decrease. 
As regards carbonic waters, it was found that the microbia decrease in num- 
ber and are always less than in the original water. This was found to be due 
to the carbonic acid, as the same effect was observed when water was charged 
with the gas, without pressure. The presence of oxygen seems not to be neces- 
sary for the increase of microbia in water, as was proved by replacing the oxy- 
gen by hydrogen. 
(To be continued ). 
Elementary histological studies of the Cray-fish.—IV. 
By HENRY L. OSBORN. 
CHAPTER I.—THE GREEN GLAND.—( Continued from page 125.) 
Record of the observations.—The biologist has, by no means, 
paiched his work when he has prepar ed and ‘examined his section; he has 
*Chem. News. Lii (1885), 52, 66, 73, 89, ror. 
+ On the Micro-organisms of Potable Waters : Their life in Carbonic Waters. Chem. News. Lii (1885), 275. 
{ Requiring only 0.99 mgr. of oxygen to oxidize it. 
