10 TRICHINA SPIRALIS. 
OF THE ORIGIN OF TRICHINE. 
There has been a great deal of speculation in regard to the origin 
of the trichina, but, as was to have been expected, with very unsatis- 
factory results. We know just as much of the origin of trichinz as 
we do of the origin of the pig, the cow, or the goat, and no more. 
That they may change their habits and some of their characteristics 
when placed under new conditions is possible; but, like every other 
animal, all the trichinz now infesting man and the domestic animals, 
are the direct descendants of others whose ancestry leads back in 
unbroken series toa point far beyond the reach of human knowledge 
orreason. Nor does it require any special hypothesis to account 
for the enormous numbers of trichinze which confessedly exist, if 
we give due consideration to known possible methods of distribu- 
tion, and to the extraordinary fecundity of this parasite. 
MODE OF DISTRIBUTION OF TRICHINA. 
Unless when man interferes with the processes of nature, the animals 
which are infested with trichine, are chiefly those which are wholly 
or partially carnivorous, like the pig, the dog, the cat, the rat, and 
man himself. And since trichine are dangerous only when present 
in any given animal in very large numbers, it is only the flesh 
of carnivorous animals that we have to fear. Of the carnivora with 
whick man comes in contact, the pig is the only one whose flesh is . 
employed for food by civilized nations, so that the rat, the cat, and 
the dog, must be left out of the direct sources of human trichinosis, 
although as propagators and distributors of.the pest, they cannot be 
safely neglected. 
It would seem that some animals, even when exposed to infection, 
do not readily harbor those objectionable guests; thus, even when 
birds and sheep have been liberally fed with trichinous meat, these. 
parasites cannot be detected in their flesh. But, in the ox, the. 
rabbit, and the guinea pig, they multiply freely, and become en- 
cysted in the flesh of these animals, ready, under suitable conditions, 
to again begin the cycle of their life history. Fortunately, however, 
the sources from which oxen and other strictly herbivorous 
animals obtain trichine are so limited that but little danger 
ever arises to humanity directly from this source, and it is only 
when other agencies come into play that the flesh of the ox de- 
mands our attention in this regard. To understand these con- 
