670 Gid. 



chronic dropsy of the ventricles must be considered, but in this 

 case differential diagnosis may be based on the absence in ccen- 

 nrosis of the acute attacks that not rarely occur in internal 

 hydrocephalus. There is a possibility of confusion with epi- 

 lepsy in those cases in which occasional attacks of general 

 spasms occur, but in epilepsy there is complete absence of any 

 evidence of brain trouble in the intervals between the attacks. 



A local diagnosis is only possil)le when there are pro- 

 nounced localized symptoms (movements in circles always in 

 the same direction, cerebellar ataxia, rolling, functional disturb- 

 ances of certain cranial nerves, Jacksonian epilepsy), and there 

 is compressibility of the roof of the cranium at one particular 

 spot, or percussion yields a hollow sound, but as mentioned 

 above, the spot does not always mark the seat of the cyst. 



The connection between the nature and direction of the forced 

 movements and the situation of the cyst, is seldom so intimate that the 

 situation of the cyst can be determined without further investigations. 

 This is true, lioth for the cases in which there is a single cyst, and in 

 eases in which there are large numbers. Comparison of large numbers 

 of results gives the following points as being common to the minority of 

 cases. In most cases, the cyst is in that half of the brain towards 

 which the forced movements are made. In cases in which the animals 

 move in circles, the cyst is situated in that half of the brain which is 

 turned towards the center of the circle and is situated close to the roof 

 of the cranium. Rotation about a tixed point indicates the presence of 

 a cyst in the depth of the opposite hemisphere, or in the floor of the 

 lateral ventricle, in which case the corpora quadrigemina are subjected 

 to pressure. In some cases movement in circles towards the sound side 

 is seen. When animals force their way forwards with the head de- 

 pressed, the cyst is as a rule, in the frontal lobes directly in front of 

 the corpus striatum ; while in cases in which there is rolling, it is situated 

 at the base of the cerebellum or on the pons. If the cyst be in one of 

 the hemispheres of the cere])e]]um, the vermiform process, or the occip- 

 ital lobe, there is evidence of great giddiness and a staggering gait. In 

 cases in which the head is drawn forcibly backwards, the cyst is usually 

 to be found in the neighborhood of the tentorium cerebelli between the 

 cerebrum and cerebellum. 



In 76 animals that were trepanned or examined postmortem Selioltz found 

 the cyst in 17 cases on that side of the brain that was turned towards the center 

 of the circle. 



Prognosis. The disease may terminate at the stage of ex- 

 citement, owing to the death of the embryos (about tw^o per cent 

 of cases, Ziirn), but prognosis is unfavorable, even in the early 

 stages. In the second stage, prognosis may be made more or 

 less favorable by surgical interference. Results obtained up to 

 the present show that provided the operation be done in time 

 about a third of the number of sheep, and in cattle under favor- 

 able conditions, not rarely a half or even two thirds of the ani- 

 mals, may be saved. 



