132 DIAGNOSIS OF POSITION OF CCENURUS CEREBRALIS. 
(3) A depressed position of the head, with a desire to make trotting 
movements, and abnormal raising of the fore-limbs, suggests that the 
site is towards the front of the hemisphere,' or in the depths of the 
hemisphere towards the corpus striatum. 
(4) Staggering, with general uncertainty of movement, points to the cere¬ 
bellum or posterior portions of the cerebrum as the position of the cyst. 
(5) The base of the cerebellum, or the pons varolii or medulla 
oblongata, is affected where the animals fall down and make rolling 
movements around the long axis of the body. 
(6) Stumbling, and frequent falling, and holding the head high (Segler), 
suggest the growth to be between the cerebrum and cerebellum. 
These conclusions are evidently not very reliable. Experience, however, 
testifies that in most cases the skull over the hemispheres must be 
selected as the site of the operation. The bladder being of considerable 
size, it is not necessary to discover its central point. Accordingly, when 
the skull gives no direct evidence of the precise site, most operators 
trephine about § of an inch behind the inner border of the horn in 
rams, and in ewes about f to J of an inch behind the horn core. The 
centre of the posterior lobe will be met by operating about f of an inch 
from the middle line. To avoid injuring the sinus longitudinalis, the 
point of operation must not approach nearer than T 3 g of an inch to the 
middle line. The best possible antiseptic precautions must be adopted. 
After opening the cranial cavity the thinned and protruding dura mater 
must be divided, and the bladder, which will generally be found lying 
below it, removed with forceps. The skin is then closed with catgut or 
silk sutures, powdered with iodoform, and covered with turpentine or 
tar. Wound gelatine is also suitable. 
Moller’s experience with trephining has not been favourable, and he 
prefers the trochar. The following is the method of procedure:—The 
animal is laid on its side on a table, the surface of the skull shorn, the 
wool removed, and the skin disinfected. In rams having large horns, 
where the skin inclines to forfn folds, this is rather difficult. The 
trochar is provided with a canula suitable to the thickness of the skull, 
that is, one in which the round shield is not much further from the end 
of the canula than the thickness of the skull, so that the instrument shall 
not enter the brain too deeply (fig. 69). With some care and practice, 
however, this appliance is not required. It must be remembered that 
the thickness of the skull varies considerably; in ewe lambs it may only 
be a few lines; in rams with large horns it is often more than | of an 
inch. The point of the trochar (previously disinfected by boiling), being 
directed rather towards the middle line and backwards, is driven through 
the roof of the skull by a few light blows from a hammer. 
The stilette is then removed, and if the bladder has been struck its 
