Jan. 31,1916 
Effects of Refrigeration on Trichinella spiralis 
851 
SUMMARY AND CONCLUSIONS 
Prior to the investigations recorded in the present paper very little 
experimental work had been done upon the effects of cold upon encysted 
trichinae, and the current belief was that low temperatures do not seri¬ 
ously affect the vitality of these parasites. This belief is shown to have 
been erroneous by the results of numerous experiments. 
Quantities of trichinous meat varying in weight from a few grams to 
nearly 400 pounds were frozen and kept for periods varying from a few 
minutes to 57 days at various temperatures below the freezing point of 
water. Usually the process of refrigeration was carried out in cold- 
storage compartments known as freezers, but in a few cases in which 
the low temperature was maintained only a short time, a freezing mix¬ 
ture was employed. In most cases the period of refrigeration was be¬ 
tween 5 and 20 days. The meat on removal from the freezer was gen¬ 
erally allowed to thaw slowly at ordinary house temperatures; in a few 
cases, in order to study the effects of rapid thawing, the process was 
hastened by breaking apart the pieces of frozen meat so that they 
thawed completely in a few minutes. Generally the meat after thawing 
was treated as follows: A portion was chopped or ground into fine pieces, 
placed in an artificial gastric juice, and incubated at 38° to 40° C. over¬ 
night, and then washed with water or a physiological salt solution by 
decanting and sedimenting. The sediment containing the trichinae 
isolated from their capsules was examined microscopically on a warm 
stage, and the number of inactive and active ones recorded, together 
with such other observations as appeared worthy of remark. For the 
purpose of controlling the effects of the process of digestion, some 
trichinous meat, nearly always from the same carcass as the frozen 
meat, which had been kept in an unfrozen condition, was digested at the 
same time, using some of the same lot of digesting fluid. Another por¬ 
tion of the frozen meat after thawing was fed to test animals, in most 
cases to white or hooded rats specially reared to avoid chances of acci¬ 
dental infection; as a rule, five rats were fed, receiving the meat on sev¬ 
eral successive days. Finally, unfrozen meat from the same carcass 
as that used in a given refrigeration experiment was fed to control test 
animals, usually in much smaller quantities than in the case of the 
frozen meat. In some instances no control test animals were fed. The 
test animals as they died, or after about a month if they lived that long, 
were examined for trichinae, the intestines as well as the diaphragm 
being examined if they died within the first two weeks after feeding; 
otherwise only the diaphragm. About 30,000 trichinae were examined 
from artificially digested frozen and unfrozen meat, and over 500 test 
animals and control animals were fed and examined. 
A considerable proportion of the trichinae in meat exposed to a tem¬ 
perature of about 15 0 F. for periods of 23 days or less survive and are 
17212°—16-3 
