6 BULLETIN 880, U. S. DEPARTMENT OF AGRICULTURE. - 
after they were received from Chicago, grinding them up together 
in a meat chopper, and washing for about two hours in running 
water. The ground meat was then fed to three or four rats or mice 
(usually rats) kept together in a single cage, an average of 10 grams 
of meat being supplied to each animal at each feeding, and three 
feedings being given on successive days. In a very few cases guinea 
pigs were used as test animals, the meat being given by forced feeding. 
As may be expected, and as was found by the results of the post- 
mortem examinations, the plan of feeding several animals together 
in a single cage does not necessarily bring about an even distribution 
of the meat among them. Differences in the total quantities of meat 
eaten by the several animals, however, tend to diminish with successive 
feedings. All the test animals used in Washington were reared 
under conditions which practically excluded prior mfections with 
trichine as they were bred at the Bureau Experiment Station and 
until used in the tests were nourished on a diet from which meat 
was excluded. 
Unless they died earlier, the test animals were chloroformed about 
‘ 30 days after the first feeding of the meat under test, and a portion 
of the diaphragm and sometimes other muscles were compressed 
between thick glass slides and examined microscopically to deter- 
mine the presence or absence of trichine. Animals that died from 
infection with trichine or from other causes within 10 days after 
the first feeding were examined to determine the presence or absence 
of intestinal trichine. If death occurred between the tenth and 
fifteenth days after the first feeding portions of the diaphragm 
as well as the intestines were examined. Animals that died after 
that period were not as a rule examined for intestinal trichine, 
examination being restricted to the musculature. Migrating larve 
that have not yet become encysted or established in the muscles 
may commonly be detected in the fluid which collects around the 
muscle as a result of compression between the glass slides, and older 
but still unencysted larvee may be seen both in the muscles and in 
the fluid surrounding the muscles. Intestinal trichine when present 
may be readily demonstrated by slitting open the intestine from end 
to end after removal of that organ to a Petri dish containing 
physiological salt solution. Scraping the intestinal mucosa with the 
dull edge of a scalpel tends to remove firmly adhering parasites. 
The parasites if present may be picked out of the dish with the aid 
of a lens, mounted on glass slides and examined microscopically for 
confirmation of their identity. 
The same technic as to post-mortem examinations of test animals 
was followed in the Chicago laboratories as in the Washington 
laboratory. 
