(59 
been stated above, the Cercaria is for a time a free swimmer and hence 
may be taken into the stomach by the sheep when drinking, or at¬ 
tached to herbage in damp places. Second, it has been ascertained by 
Yan Beneden, that some species of this group pass to the mature state 
directly from the Heclia stage without undergoing the intermediate or 
cercaria stage, as these are free they may be taken into the stomach 
in water or on damp herbage. 
As before stated, these internal parasites are supposed to be the 
cause of rot in sheep, though many persons are inclined to believe 
they are a consequence, rather than cause, of disease. But all appear 
to agree that this disease is connected with the condition of the soil, 
or state of the weather, moisture being the element most likely to 
produce it. This corresponds exactly with the theory of its life-history 
which I have presented, and indicates the best means of preventing 
it, to-wit: give them well-drained, open, airy pastures, and proper pro¬ 
tection in damp and rainy seasons. It is more than probable the con¬ 
dition of sheep is often attributed to this disease, when it is due to 
other causes. Randall asserts that he has never witnessed an instance 
of rot in the United States; yet I notice in the annual reports of the 
National Agricultural Department statements of large numbers dying • 
annually of this disease. 
For the numerous remedies which have been suggested, I refer you 
to the various works on sheep, and to the veterinary surgeons, 
HYDATID OF THE BRAIN ( Coenurus cerebralis). 
Another very singular and fatal disease, known as turnsick, staggers 
and sturdy, or more correctly, “Hydatid of the brain,” is caused by a 
parasitic worm belonging to the same class as that just mentioned, 
but to the order Cestoidea , or Tape-worm group. On examining the 
brain of a sheep which has died from this disease, a watery bladder, 
sometimes quite small, at others as large as a hen’s egg,' is found, 
It possesses a number of heads, which are distributed over the bladder, 
each having an oval orifice, surrounded by minute, sharp hooks, 
within a ring of sucking disks. On account of its numerous heads, 
it has sometimes been called Hydatis polycephcdus cesebralis , or the 
many-headed Hydatid of the brain. With the sucking disk, they 
fasten themselves to the brain, and, by means of their hooklets, which 
appear to be a kind of ciliae, it is supposed they imbibe food. The 
fluid of the bladder is usually clear, but sometimes turbid, when, if 
carefully -examined with a miscroscope, it will be found to contain a 
number of minute, worm-like bodies or animalcules. 
It has now been ascertained that these cystle or bladder worms, so far 
as their history has been traced, or early stages in the lives of tape¬ 
worms, these heads which are seen attached to the-bladder ultimately 
forming the head of the tape-worm. 
