ON HYDATIDS IN TIIE SHEEP. 
525 
wire cannot possibly reach them all. I am afraid that this 
celebrated operation, and which the name of the Ettrick shepherd 
for a while rendered popular, must be suffered to sink into com¬ 
parative disuse and distrust. 
The Situation of the Hydatid discovered.— The effect of pres¬ 
sure is not always sufficiently understood in veterinary or human 
practice. By the constant but slight pressure of this bladder, 
not only is a sufficient portion of the brain absorbed to make 
room for the growth of the hydatid, but even the bony substance 
of the roof of the cranium disappears ; and therefore, in process 
of time a soft yielding spot, somewhat variable in its situation, 
but generally a little anterior to the root of the horn, and more 
towards the centre of the skull, marks the residence of the 
hydatid. 
In this way alone is the precise residence of the hydatid de¬ 
tected; and I must beg leave respectfully to demur to the account 
of this matter given by a very excellent writer, Dr. Kerr, in 
the “ Cyclopedia of Practical Medicine/’ that “ their precise 
situation" in this (the cranial) cavity has been frequently dis¬ 
covered by the effects produced on particular nerves, and the 
action of those parts under their influence ; indications which 
have sometimes led to their extraction, to the perfect relief of 
the suffering animals.” Anatomically speaking, I am at a loss 
to conceive how they can, by possibility, influence the function 
of any of the cerebral nerves, so as to guide me to their “ precise 
situation,” or how I should be able to reach them there. No 
partial (and it would only be a partial) impairment of smelling, 
vision, or hearing, or of the motion of the muscles of the eye, 
could be recognised by me: but it is only by the uncertainty of 
gait and the growing stupidity, that I can recognise the injurious 
action of some foreign body on the sensitive and the motor 
columns generally, or the prolongation of them within the cra¬ 
nial cavity. It is a sense of uneasiness or pain, or a feeling 
of weight, that inclines the animal to relieve himself by leaning 
the head on one side, and thus pointing out to us the lobe in 
which the parasite is lodged. The circular motion, naturally 
tending to that side from this inclination of the head, confirms 
this indication: but it is the softening of the skull which alone 
enables us to determine in what part of the lobe we are to seek 
for the author of the mischief. And now another kind of ope¬ 
ration can be performed, to get rid of this little but formidable 
being. 
The Operation of extracting the Hydatid .—A crucial incision 
should be made over the spot. If a portion of bone remains, it 
should be removed by the trephine ; or if the bone is quite gone, 
VOL. VII. 3 Y 
