70 
Prof. Huxley has presented strong reasons for believing that the 
minute worms seen in the bladder ultimately become the joints of the 
tape-worm, each of which, in turn, is capable of producing under fav¬ 
orable circumstances, another cystic, or bladder-worm. But the strange 
part of the history of these similar animals is the fact that these two 
stages of life cannot occur in the same animal; or, in other words, 
the cystic or bladder-worm in one animal will never develop into the 
tape-worm, until it passes into another animal. For example, the 
bladder-worm found in the flesh of the hog becomes the tape-worm 
in man; the bladder-worm of mice becomes the tape-worm in the cat; 
that of the hare the tape-worm of the fox; w 7 hile that w T hich produces 
hydatids in man becomes the tape-worm in the dog. 
Taking these facts as a guide, I am led to believe that the bladder- 
worm found in the brain of sheep is but the early stage of a tape¬ 
worm found in some other animal; probably the wolf, dog, or some 
carniverous animal. How it escapes from its bony prison, or is taken 
up, I do not know; but they are very tenaceons of life, and may pos¬ 
sibly pass into the stomach of other animals long after the death of 
the sheep, and still be developed. It is possible the history of this 
species has been traced; but, if so, I am not aware of it. 
No adequate remedy has so far been found, nor is it likely there 
will be; but, fortunately, its occurrence in this country aj)pears to be 
rare. 
In addition to the foregoing, there are a few other parasites which 
occasionally infest sheep to an extent sufficient to do them considera¬ 
ble injury. Of these I simply mention the following: 
Taenia plicata; or, the folded tape-worm. I am unable to give the 
history of this species; nor am I aware that it has ever been ascertained. 
From what we know of the life-history of other species, it is difficult 
to account for the presence of a tape-worm in a purely herbivorous 
animal. So far as known, the cystic, or bladder-w r orm, which is the 
young or preliminary stage of the tape-worm, is always found in a dif¬ 
ferent animal from that in which the mature tape-worm occurs. 
Ascaris lumbricoides .—The round worm of the intestine. These are 
worms w 7 hich inhabit the small intestine; and, according to Mr. Spooner, 
on whose authority they are introduced here, it would appear to be 
the same species as that in man; but it is more than probable that 
the nematode worm observed was some other species of ascaris. These 
species are said to give rise, especially in lambs, to severe diarrhoea. 
The foregoing is but a partial list of the insects and other parasites 
that infest domestic animals; and is given here because of the fre¬ 
quent calls on me in reference thereto. This is a subject that belong s 
more properly to the Veterinary Surgeon. 
