68 STORRS AGRICULTURAL EXPERIMENT STATION. 
\ 
EXPERIMENTS NOS. 7, 8, 9. 
In the three following experiments the observations were 
extended in two directions. 1. ‘The attempt was made to 
differentiate the species of bacteria more thoroughly upon the 
plates, and in the tables given below a larger number of different 
types have been separated from each other, and their numbers 
determinedas far as possible. It will be evident from the tables, 
however, that these additional determinations of individual 
species do not affect the general problem, for the new species 
which are tabulated constitute only a very small proportion of 
the whole, while in all cases the types already referred to in the 
previous tables constitute the large majority. 2.. The chief 
purpose of these three experiments was to extend the observa- 
tions to milk kept at lower temperatures than those used in 
previous cases. ‘To this end, one of the compartments in a cold 
storage plant was used for keeping one of the samples of milk. 
The temperature in this compartment was about 1° above freezing 
point, varying very slightly during the series of experiments, 
and probably never rising above 1°. Wefound that milk can 
be kept at this temperature for a long time, and that for many 
days it appears to be perfectly normal. It has already been 
shown, however, that bacteria will grow even at these low 
temperatures. Experiments on this subject have already been 
carried on by. quite a number of investigators. Havemann 
(Ueber das Wachstum von Mikroorganismen bei Eiskranktem- 
peratur. Inaug. Dis. Rostok, 1894) showed their growth at 0° 
in water; Glage (Zeit. f. Fleisch u. Milch hyg. XI. p. 131) 
found them to grow at this temperature in flesh. (Other refer- 
ences to similar observations are: Schmidt—Nielson, Cent. f. 
Bact. u. Par. IX. p. 145; Schmelk, Cent. f. Bact. u. Par. IV. 
p. 545; Conradi & Vogt, Zeit f. Hyg. XXX. p. 287; Fischer, 
Deut. Med. Woch, 1893; Muller, Arch. f. Hyg. XLVII. p. 127). 
The experiments hitherto performed have been almost wholly 
confined to a quantitative determination of bacteria, and have 
consisted in placing samples of culture material at a temperature 
of 0°, or a little above, and making quantitative determinations 
at various intervals. ‘The result of this work in general has 
been to show that, even at a temperature of practically freezing, 
there is a growth of bacteria, which, though slow, may be con- 
siderable. ‘The question of the £zzds of bacteria that develop 
