DIAGNOSIS OF POSITION OF CffiNURtTS CEREBRALIS. 383 



satisfactory treatment. Even in the previous century this was 

 attempted by laymen in a primitive way with the pocket-knife, 

 but success could only be satisfactorily attained when proper in- 

 struments had been constructed. These consist of a small trephine 

 about f of an inch in breadth, or of special trocars, which have been 

 perfected by Zehden. 



It is of primary importance to fix the position of the cyst (or 

 cysts). This is usually in the neighbourhood of the surface of one 

 hemisphere of the brain. Sometimes it can be recognised by the 

 softness and yielding of the bone on strong pressure. Percussion 

 gives a dull sound over the affected spot, a symptom to which 

 Villborg directed attention last century. But these signs are often 

 entirely wanting, and the position of the parasite can only be con- 

 jectured from noting the peculiarities of the patient's movements. 



(1) Where the patient shows turning movements, with the head 

 inclined to one side, the cyst generally lies on the surface of one 

 hemisphere, and on the side towards which the animal turns. 

 Though this symptom, according to Moller's experience, is by far 

 the most reliable, exceptions occur, especially where the cyst is 

 large, and presses on the deeper-lying portions of the brain. 



(2) Twisting of the head towards the hind-quarters points to 

 the cyst lying in the depth of the hemisphere of the same side, or 

 in the base of the opposite ventricle. 



(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 cerebellum or posterior portions of the cerebrum as the position 

 of the cyst. 



(5) The base of the medulla oblongata, or the pons varolii or 

 cerebellum, is affected where the animal falls down and makes rolling 

 movements around the long axis of the body. 



Experience, however, shows that in most operable 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 § to f of 

 an inch behind the horn core on the side to which the head is 

 inclined. To avoid injuring the sinus longitudinalis, the puncture 

 must not approach nearer than ^ of an inch to the middle line. 

 The best possible antiseptic precautions must be adopted. After 



