852 
Journal of Agricultural Research 
Vol. V, No. 18 
quite lively after thawing, but such meat frequently fails to infect test 
animals. This temperature is injurious to trichinae, but its effects are 
uncertain, and meat exposed as long as 23 days has proved to be infec¬ 
tious. Some of the trichinae in meat exposed to a temperature of about 
io° for periods of 57 days or less generally survive, but the meat fre¬ 
quently fails to infect test animals. A temperature of io° is more inju¬ 
rious to trichinae than a temperature of 15 0 , but, like the latter, its effects 
are uncertain, although meat exposed to it for 14 days or longer has 
generally failed to produce infestation; or if infestation resulted it was 
slight. No infestation has been produced by trichinous meat exposed 
to a temperature of about io° for 20 days or longer. 
Apparently in the neighborhood of io° F. a critical point is reached 
below which the effects of cold upon trichinae become suddenly much more 
pronounced. 
Temperatures of 5 0 F. or lower profoundly affect the vitality of tri¬ 
chinae. Only a very small proportion survive an exposure of more than 
five days, and these are so seriously affected that infections are very 
unlikely to result. Slight infections, however, have resulted from meat 
exposed to a temperature of — 9 0 to o° for 10 days. 
Trichinae from meat exposed to temperatures below 15 0 F. when exam¬ 
ined microscopically after thawing exhibit changes in the appearance of 
the protoplasm. A temperature of io° produces greater changes than 
15 0 , and the changes produced by a temperature of 5 0 are still more pro¬ 
nounced. The more conspicuous of these changes are more or less loss 
of color of the esophageal cell body, more or less solidification of its nuclei, 
abnormal granulation of its protoplasm, and more or less dissociation 
and rounding of the germ cells. 
Trichinae vary in their resistance to cold, and some individuals survive 
refrigeration longer and at lower temperatures than others. 
Within certain limits the rapidity with which trichinous meat freezes 
or thaws has no appreciable effect upon trichinae. Apparently the rapid 
freezing and thawing undergone by very small pieces of meat (a few 
grams in weight) adds to the injurious effects of refrigeration, but the 
natural variations in the rate of freezing and thawing dependent upon 
variations in the quantities of meat frozen between limits of half a pound 
and several hundred pounds do not noticeably modify the effects of 
refrigeration upon trichinae. 
The vitality of trichinae which survive refrigeration does not decrease 
noticeably during a period of at least a week after the thawing of the 
meat. 
The artificial digestion of trichinous meat for 24 hours at a temperature 
of 38° to 40° C. in a fluid consisting of water, 1,000 c. c., hydrochloric 
acid (sp. gr. 1.19), 10 c. c., scale pepsin (U. S. P.), 2.5 gm., and sodium 
chlorid, 5 gm., has no apparent effect upon the activity or structure of 
the trichinae, released from their capsules by the process of digestion. 
