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He points out, however, that the presence of some thousands of germs per c.c. would be held to
condemn water, and, inasmuch as ice generally contains a smaller number of germs than the
water from which it is made, it may be safely assumed, if the ice contains many organisms, that
the original water was quite unfit for use. Fraenkel found the number of living bacteria in a
sample was sometimes reduced as much at 90 per cent, by freezing for three or four days, but that
the ice might still contain large numbers if the water had been greatly contaminated with them.
Crystal-ice prepared from distilled water was ascertained by Fraenkel to be almost free from
germs, and he conclndes that if ice were always eaten, this last sort of ice alone should be allowed
to be sold. Ice, however, as he notes, is largely used as a cooling agent and preservative, and provided
it does not come into contact with food, he sees no reason for insisting on its purity. As he
says, examination by the eyes and nose of an ordinary ice-chest1, which has been a fortnight in
use, suffices to demonstrate how much dirt ice contains. He then proceeds to point out that fish,
vegetables, etc., are laid upon ice, and that raw ice is actually added to beverages, and he says, if
it be deemed desirable to avoid Spree water or bad spring water in wine, all ice save that made
from distilled water must be avoided. Of course, the use of pure ice is to be recommended for
medicinal purposes. Hence Fraenkel finally concludes that natural ice is unfit for consumption
in beverages, or for use medicinally, or for application to wounded surfaces. If it be a question
merely of contact with foods which are afterwards cooked, raw ice may be permitted, though pure
ice is even then to be preferred. Raw ice may be used when the cooling agent does not come into
actual contact with the food.
Dr. T. Mitchell Prudden's report " On Bacteria in Ice and their relation to Disease, with
special reference to the Ice supply of New York City," appeared in the Medical Record, Vol. 81,
1887. Dr. Prudden experimented with six different species of micro-organisms, and found the
effect of freezing on the numbers recoverable on cultivation was in the direction of marked diminution,
but the germs did not always disappear altogether. He tried alternate freezing and thawing,
and the results were more striking, the organisms being completely destroyed in a short time. He
further experimented with low temperatures, under conditions in which the water was not allowed
to crystallise into ice; by coating the inside of test tubes with sterilised sweet oil, he found it was
possible to cool small quantities of water placed in the tubes considerably below freezing point
without occurrence of solidification, provided the water was kept perfectly still; it is, of course, well
known that fluids crystallise more readily when in contact with rough than with smooth surfaces.
Dr. Prudden compares the effects produced under these conditions with those of ordinary freezing,
and remarks that the " different destructive capabilities of what may be called dry and moist cold
are interesting in view of the similar differences which exist at the other end of the scale between
dry and moist heat." He concludes that water which contains bacterial contaminatian "by freezing
and remaining frozen for a few days may purify itself by the destruction of as much as 90 per cent,
of the bacteria "; further, that the " number of living bacteria is gradually reduced in ice," but
" this reduction does not go on to extinction."
By way of practical illustration, he refers to the New York water supply, and says: " He, who,
impressed with the importance of a pure drinking water, should perfectly filter half a glass of
average Croton water, and then add to it an equal quantity of the average ice, would have the
satisfaction of replacing the bacteria removed, with more than eight times as many from much
more uncertain an questionable sources.
The reduction in numbers of typhoid bacilli in ice was made the subject of experiments by
Sedgwick, Winslow and Park (Boston Medical and Surgical Journal, CXLV., p. 556). They found
that beginning with a certain number of typhoid bacilli in the ice, after three weeks the percentage
dead was 99"5 : this being also the percentage purification achieved in an ordinary water filtering
plant. Hence they argue that ice known to be definitely infected with typhoid bacilli might, after
standing three weeks from the date of freezing, be consumed with no more danger than that
involved in drinking infected water after efficient filtration. It is noted, moreover, loc. cit. the
" mere act of freezing itself results in the diminution by 90 per cent, at least, by physical throwing
out of the bacteria." The reporters of the outbreak of enteric fever due to ice referred to on page 5,
point out that but little regard can be paid to considerations such as those which have just been
adduced.
An important light upon the bacteriology of ice was thrown by Professor Abba2, who sought
to reconcile the alleged absence of interference with the life processes of bacteria upon exposure to
low temperatures, with the observed diminution in the number of organisms in ice. He quotes the
results of Belli'1, who, using liquid air, exposed anthrax and fowl-cholera bacilli to temperatures
of from—180° to—190° C., without causing perceptible impairment of their pathogenic
property, and in the light of these experiments Abba is driven to conclude that the
diminution of organisms associated with freezing is brought about not so much by their
destruction as by their being extruded from the ice. In order to put the matter
to the test he caused 25 litres of water containing 8 per cent, of chloride of sodium to be
frozen into a parallelepiped of ice, the outer part of which consisted of clean ice, the inner
axial portion, that last frozen and therefore containing the solid matters expelled from the ice as
freezing proceeded, being quite opaque. Examination of specimens of the clear and opaque ice
showed the former to bo free from chloride of sodium, while the latter on being melted gave a rich
1 " Any sort of ice is good enough for the homo ice-box. It melts there, and the same heat whioh melts it
lets loose its tenors into the meats, butter, and other food substances whioh form the contents of the refrigerator.
Half the time the ice-box is neyor scalded or sterilised."—Oold Storage, 15th August, 1904.
2 Uebor dem Mechanismus der biologischen Selb»trei*igung des Eises."—Zeitschrift fur Hygiene und
Infectionskrankheiten. Band 45, Heft II.
3 Biforma Mtdica, 1901.