PARASITES OF ANIMALS. 87 
to correspond to one of the withdrawn and inverted worms, 
as represented in Figure 64. 
Each little worm has a head with a circle of hooks in the 
middle, surrounded by four suckers, just as in the measle- 
worm of pork. In this case, each little worm with a head is 
the larva of one of the dog tape-worms ( Tenia cenurus), 
but in this the young worms have the power of propagating 
themselves by a kind of budding, in a manner similar to that 
by which the coral-animals bud from each other and so 
build great colonies. Thus it is that one of these little 
worms, lodged in the brain, by budding produces hundreds of 
others like itself, all connected together by the membrane of 
the sac; and thus the tumor constantly grows larger, instead 
of always remaining small, as does the measle-worm. 
Lffects. 
Now, if a dog gnaws a skull containing such a tumor, and 
swallows the whole cyst, or any part of the membrane that 
has heads on it, the heads will be liberated from the mem- 
brane, and each one will fasten to the lining of the dog’s 
intestine by means of its suckersand hooks. There they will 
rapidly grow larger and larger ; new joints will be formed for 
the body, and in the course of three months each one will become 
a small tape-worm, with many joints, and each of the larger 
joints will have both male and female organs, and will be 
capable of propagating the race by itself. The female organs 
of each joint contain thousands of eggs, which are discharged 
when mature, and passing from the intestine of the dog in 
large numbers, they will be scattered about freely over the 
pastures and fields wherever the dogs go. Ifa lamb or sheep 
accidentally swallows some of the eggs with grass or in water, 
the eggs will hatch in the stomach intominute worms. These 
force their way, by means of their six little hooks, through 
the lining of the intestine into the blood-vessels, and are thus 
carried to different parts of the system; but usually only 
those that lodge in the brain live, and there excavate galleries 
(Figure 65) and grow, and bud, thus forming the ‘“ water- 
brain,” and finally kill the sheep. Cenuwrus cysts have been 
observed, however, beneath the;.skineof sheep, in the cellular 
tissue. Similar cysts have, also, been found in the liver 
