850 
Journal of Agricultural Research 
Vol. V, No. 18 
TEST ANIMALS 
It will be noted from Table I that of the 54 test animals (53 rats, 1 
guinea pig) fed with unfrozen meat as controls upon the animals fed with 
frozen meat, only 3 failed to become infested. The rats fed as controls 
in experiments 72 to 76 are left out of consideration, as they were not 
fed until nearly eight months after the slaughter of the hog from which 
the meat was taken. Examination of some of the meat artificially 
digested nine months after slaughter of the hog showed that the trichinae 
were dead. One out of three rats fed as controls in experiments 23 to 34 
showed no infection, the two others being heavily infested. Out of 29 
rats fed as controls in experiments 65, 65a, and 67 to 71, 1 showed no 
infection, 27 of the remaining 28 showing heavy infections. Finally, 1 
out of 12 rats fed as controls in experiments 91 to 126 showed no infection, 
but this one was killed four days after feeding for another purpose and 
as only a small portion of the intestine was examined, trichinae may have 
been present and were not discovered; 8 of the remaining rats were 
heavily infested; in the case of the 3 others the degree of infestation was 
not recorded. 
These results, particularly in view of the fact that the control animals 
as a rule received much smaller quantities of meat than those fed on meat 
which had been frozen, demonstrate the adequacy of the methods em¬ 
ployed in feeding test animals. The results of the later experiments, how¬ 
ever, beginning with No. 23 are considered more reliable, so far as the 
feeding tests are concerned, than those of the earlier experiments, as more 
animals were used and care was taken to feed larger quantities of meat. 
The method of feeding each lot of test rats together in a cage a certain 
amount of meat on several successive days, followed in most of the experi¬ 
ments, appeared to be quite satisfactory. Undoubtedly some of the rats 
in each lot ate more of the meat than others, so that some inequality in 
the degree of infestation of the rats would be likely, which, however, was 
of little importance, as the results of the feeding tests were judged upon the 
basis of the findings in all of the rats in each lot. The use of a number of 
rats for each test allowed larger quantities of meat to be tested, which gives 
a decided advantage over the use of a single animal. For the same reason, 
rats are preferable to guinea pigs, as they will eat of their own accord much 
larger quantities of meat than can readily be fed to guinea pigs forcibly 
or by mixing with lettuce, cabbage, etc. Furthermore, it is difficult to 
induce guinea pigs to eat chopped meat mixed with lettuce or other 
materials if the meat has become only slightly tainted, whereas rats 
usually eat meat readily even after it has become very stale or partially 
decomposed. 
