i88o.] 
Internal Enemies . 
305 
when they enter our stomachs, instead of submitting, as 
does lifeless matter, to the digestive process, not merely 
retain their vitality, but undergo their normal development 
reproduce and multiply, and devour us in an almost litera 
sense of the word. 
Amongst the most dangerous of these parasites is one 
which has only been known for about thirty years— -the 
Trichina spiralis. This pest is at present far from uncommon 
in the flesh of swine, and now constitutes a very definite 
danger for the consumers of pork and bacon. It must not 
be inferred, as it is by many persons, that the Trichina sud- 
denly sprang into being about the year 1850 from what was 
previously lifeless matter. It is perfectly possible that it 
may have existed in the swine for untold centuries, but that 
it was not detected and characterised as a distindt parasitic 
species. It is again conceivable that, though not recently 
called into existence, it may only of late years have found 
its way into the body of the pig. Some authorities, indeed, 
contend that its original home is that animal which Water- 
ton always called the “ Hanoverian,” i.e., the rat, but which, 
as it appears to have entered Western Europe from the 
plains of the Wolga, may claim another nationality. Rats, 
as is well known, will visit pigsties in the hope of plunder, 
and may no doubt be occasionally snapped up and devoured 
by pigs, which are semi-carnivorous animals. Whether 
every trichinised pig must at some period of his life have 
devoured a rat, or whether the parasite can be introduced 
into swine by some other channel, passing for instance from 
the mother to her young, is not quite decided, though the 
latter supposition is by no means out of the question. 
A young hippopotamus which died in captivity has been 
found to be infested with Trichince. Hence the question has 
been raised whether the rat theory is correct, and whether 
the Pachydermata as a family may not be the original home 
of the Trichince. 
It may here be remarked that rats have been gravely 
recommended as an important article of human food. A 
writer in a daily paper, not very long ago, gravely declared 
that the man who died of starvation so long as rats were to 
be had for nothing deserved severe punishment. How to 
escape the danger of swallowing Trichince was a thing not 
dreamt of in the philosophy of the humane enthusiast. 
But revenons a nos cochons , if we may so far parody the 
proverb. 
Suppose the Trichince have safely landed in the stomach 
of the pig, their career is somewhat remarkable. In the 
