Nervous, impulsive disturbance is most readily noted when the animals are at liberty. Even when the sight remains, they seem quite incapable of avoiding obstacles or as though absolutely forced to move to the right or left, etc.
Attacks of giddiness, moreover, are not unusual under the influence of the slightest excitement. During such attacks the animals thrust the head against a wall, or they involuntarily recoil or make lateral movements. In many cases these vertiginous attacks end by the animal falling and showing epileptiform convulsions, during which it may die.
The symptoms are never the same in two different animals, but they may easily be classed according to the above indications. The indications furnished by the condition of the eyes and by the peculiar impulsive movements are particularly significant.
On the other hand, there are modifications in breathing without apparent local cause, and difficulty or even impossibility of swallowing, etc., although there exists no material obstacle.
Diagnosis. The condition is often confused with meningitis, and the mistake is not serious, because meningitis and encephalitis frequently accompany one another.
Prognosis. The prognosis must be regarded as fatal. The patients very seldom recover, and there is no reason for keeping them alive.
Treatment. Here, again, blisters may be applied to the upper extremity of the neck, or setons may be passed. Cooling applications to the cranial region have also been suggested. None of these methods produces more than a temporary palliative effect.
CEREBRAL TUMOURS.
The brain may be injured and compressed by various tumours of other than parasitic origin. Such tumours may originate in the bones, the meninges or the choroid plexus, or they may simply be due to generalisation of a previously existing tumour. Whilst of very varied origin and nature, all tumours of the cranial cavity have one common effect, viz., to compress the brain. This continuous compression causes progressive atrophy of the brain, but its existence is not always suspected, because the lesions may not give rise to any marked symptoms.
The hind portions of the hemispheres and the white substance are generally very tolerant. The front portions, on the other hand—the frontal lobes and the grey substance—resent compression, which provokes various symptoms in consequence.