1050 A. F. Vass 
day. This was followed by a more rapid increase until the highest point 
was reached on the twenty-seventh day. On the thirty-fourth day the 
counts were about equal to those on the fourteenth day. 
Hammer (1912) concludes from his studies with stored ice cream that 
there is no increase in the number of bacteria during storage, as judged 
by the number of organisms developing on agar with an incubation tem- 
perature of 37° C. He assumes, of course, that the product is kept 
properly hardened. 
Gordon, Prescott, Heinemann, and Pease (1914) noted a marked 
increase in the bacteria counts of fresh ice cream over the counts of the 
mix as it entered the freezer. 
Esten and Mason (1915) concluded from their investigations that when 
ice cream is kept frozen for periods of at least a month, there is no marked 
increase or decrease in the bacteria count as shown by litmus lactose 
gelatin plate counts. 
Ellenberger (1919) noted an increase due to the freezing process, which 
he thinks may be accounted for by the breaking-up of the clumps of 
organisms by the beating received from the dasher during freezing. He 
observed no radical change in the total number of bacteria in ice cream 
during storage. The groups of bacteria in ice cream as determined by 
litmus gelatin plates and litmus milk tubes did not change noticeably 
during storage. 
CAUSE OF DEATH OF THE CELL 
Several theories have been suggested to explain the specific action 
which results in the death of the plant cells when exposed to low 
temperatures. Du Hamel and Duffon (1737) advanced the theory that 
death was due to the bursting of the cell wall as a result of the expansion 
accompanying ice formation. Senebier (cited by Géppert, 1830) also sup- 
ported this view, which was later disproved by Sachs (1860) and Nageli 
(1861). The formation of ice crystals within the cell and in the inter- 
cellular spaces was noted by Géppert (1830), but in no case could he 
find ruptured cells. He considered death a result of freezing, and as being 
in no way affected by the rate of thaw. Sachs concluded from his results 
that the degree of killing of plants at a given temperature depended on 
the rate of thaw. 
Miiller-Thurgau (1880) and Molisch (1897) were unable to detect any 
great difference in the amount of killing due to the difference in rate 
