PARASITES OF ANIMALS. , 111 
biting and snarling at its companions, but is usually too weak 
to defend himself, if attacked in return, and is easily thrown 
down. Finally the weakness increases until the poor crea- 
ture is unable to walk about, or to stand. This parasite will 
probably yield to the same remedies used for tape-worms, or 
those employed against the common round-worms of man (As- 
caris lumbricoides), to which, therefore, the reader should refer. 
NEMATODES. 
(Round-worms and Thread-worms.) 
The Flesh-worm (Trichina spiralis Owen). Figure 76. 
This mostimportant and most dangerous of all human para- 
sites, is a very minute round worm, which in the larval state 
lives in the muscles of man, swine, dogs, cats, rats, mice, 
rabbits, Guinea-pigs, and many other animals, and in the ma-. 
ture state inhabits the intestines of the same animals. The 
body is slender, smooth, and round. The intestine is com- 
posed of a series of small, bead-like swellings, separated by 
constrictions. The male is much smaller than the female, 
when mature measuring only 7s of an inch ; its body is filiform, 
pointed at the head, enlarged at the opposite end, generally 
somewhat bent or curved upon itself; the head is very small 
and pointed, unarmed, but with a minute central mouth ; the — 
posterior end of the body is furnished with a bilobed ap- 
pendage, the anal opening being between the lobes; the penis 
is a single spiculum, cleft above so as to have a V-shaped out- 
line. The female is stouter than the male and longer, meas- 
uring about $ ofan inch, when mature; the posterior end is 
bluntly rounded; the genital orifice is at about a fifth of the 
length from the anterior end of the body. They are viviparous 
and the uterus occupies most of the body, in the form of along 
and wide tube, in which the embryos are closely packed. The 
eggs are yoy of an inch long. The young Trichinz, like young 
tape-worms, occur imbedded in the muscles of the hog and 
various other animals, and man. But unlike the young tape- 
worms or ‘‘ measles,” the young Trichine are so small as to be 
quite invisible to the eye, and millions of them may ex- 
ist in the flesh of a pig without producing any unusual appear- 
ance in the meat suffieiémtite attractthe attention even of an 
