Jan. 31,1916 
Effects of Refrigeration on Trichinella spiralis 
841 
From the foregoing it appears that the results of exposing trichinous 
meat to temperatures of about o° F. are similar to those produced by 
temperatures of about 5 0 —i. e., a few trichinae may survive exposures to 
such temperatures for 6 days or more, but their vitality will be so greatly 
reduced that there is little likelihood of their causing infection, although, 
on the other hand, slight infections may result from meat exposed as 
long as 10 days. 
A good example of the relative effects of different low temperatures 
upon the vitality of trichinae is supplied by experiments 91 to 126. In 
these experiments approximately equal quantities of trichinous pork 
from the same source (mixture of meat from six hogs) were exposed for 
10 to 23 days in three freezers at temperatures of about 15 0 , io°, and 
5 0 F., respectively, a can of meat being removed from each of the three 
freezers after 10 days' exposure, another after 11 days, and so on (no 
cans, however, being removed on the twelfth or nineteenth day). It will 
be observed from the recorded results (Tables I, II) that many of the 
trichinae in the meat exposed to a temperature of about 15 0 survived, 
and up to the twentieth day of exposure were mostly quite lively after 
thawing. Some of those from meat exposed for 22 days were observed 
to be quite lively, and those which survived in meat exposed for 23 days 
were found to be fairly lively. From the results of the feeding tests there 
appeared to be a considerable reduction in the vitality of the parasites 
after 17 days' exposure, notwithstanding the survival of a large percent¬ 
age. Most of the rats fed meat exposed to about 15 0 for 10 to 16 days 
became heavily infested, but the 17-day meat failed to infect one out of 
five rats, and only two of the four others became heavily infested, the 
18-day meat failed to infect one out of five, the 20-day meat failed to 
infect one, the four others becoming only slightly infested, none of the 
rats fed 21- and 22-day meat became infested, and the 23-day meat failed 
to infect two and produced only light infestations in the three others. 
In the case of the meat exposed to a temperature of about io° F. it 
was observed that the trichinae which survived were relatively less 
numerous, as a rule, than in the case of the meat exposed to about 15 0 , 
and it was generally noted that they were less active than normal, or 
sluggish, sometimes very sluggish. The test rats, fed meat exposed for 
10 days, all became heavily infested, all five fed 11-day meat became 
infested, but one was only slightly infested, all five fed 13-day meat 
became infested, but only one was heavily infested, three out of five fed 
14-day meat became infested, but these only slightly, and none of the 
rats fed meat exposed to about io° for 15 days or longer became infested. 
In this series, therefore, there was apparently a considerable reduction 
in the infectiousness of the meat beginning with that exposed for 13 
days, and after 2 days more the infectiousness became nil. 
Practically none of the trichinae in the meat exposed to a temperature 
of about 5 0 F. (experiments 91 to 102) survived; although living trichinae 
