Tlie Natural History of Parasites. 
599 
of animals, find a proper habitat tliere, become fully developed, and de- 
posit in turn theii- ova, wbicli are subsequently carried out of the body 
through the ordinary excretions. Entozoa are so nimaerous that it is 
necessary to classify them in order to understand anything about 
them. Some years ago he made such a classification, which, although 
it might not meet all the wants of the naturalist, may claim the 
character of simplicity, and of meeting the requii-ements of the pa- 
thologist ; it is with this that we have chiefly to do to-day. Those 
creatures come, first, under the head of the protelmintha ; secondly, of 
stcrelmintha ; and, thirdly, of coelelmintha. Under the first of these 
heads we have the lowest forms of worm-life, hydatids. One speci- 
men before us has been removed from the brain of a sheep during life, 
and the animal is doing well. The class includes the acephalocyst, 
the hydatid designated by the late John Himter the pill-box hy- 
datid. Then there is the hydafis tenui-collis, or long-necked hydatid, 
which is always found attached to the external parts of organs, 
and is apparently the most harmless of all the hydatids that atifect 
an animal. Next comes the liydatis cellulosoe, so called because it lies 
in the cellular tissue which connects the muscles together in different 
paits of the body. It is this hydatid which produces that peculiar 
condition in the flesh of a pig known as measly-pork, an affection to 
which the attention not only of natui'alists, physiologists, and pa- 
thologists, but of the Government, was called during the Crimean war, 
because it was found that large quantities of measly-pork were being 
exported to supply our troops, the use of which must have resulted in 
producing tape-worms in the intestines of those who ate it. This 
term, " mcasiy-pork," is an imfortunate one, inasmuch as it does not 
indicate the nature of the malady, and indeed is apt to lead to a 
A^Tong imjjression. No two things can difler more widely than a measly 
condition of the flesh of an animal and the eruption on the skin of the 
iuman subject, properly termed measles. In many respects our no- 
menclature is defective, and this is one special instance. The ccenurus 
cerehndis. already referred to as being found in the brain of the sheep, 
received its name from the circumstance that the creature possesses a 
large number of sucking discs, or heads ; and the word cerebralis in- 
dicates that it locates itself within the brain. It is this creature 
which produces giddiness in the sheep. Lastly, there is the hydatid 
to which is given the name echinococcus, which also exists very exten- 
fiively in domesticated animals, and when inhabiting the internal parts 
produces serious diseases in the organs. 
Solid Woems. 
Among the sterelmintha, or solid worms, are included all the tape- 
worms. One specimen of this class now before him was found in the 
sheep, and another in the horse. The latter is an interesting variety, 
termed the iania mcgalocephalus from the circumstance of its having a 
large head. Another, called the iccnia scrrata, from the serrated or 
eaw-like margins of its body, is probably identical with the t(tnia 
solium in the hiunan subject. And auuther most interesting and very 
