Atrophy. Paralysis of the Optic Nerve. 447 



nection with inflammatory exudation or blood extravasation on, 

 in, or beneath the retina. In other cases the lesion is in the 

 papilla which is inflamed and swollen with the woolly aspect 

 characteristic of choked disc. In others there is congestion of 

 the optic nerve behind the bulb, with exudation into its substance 

 or beneath its sheath, or the nerve has already undergone exten- 

 sive atrophy with thickening of its neurilemma. In other cases 

 there, is atrophy of the arteria centralis retinae, or tumors of the 

 orbit or optic foramen pressing upon the nerve. Cases of this 

 kind are reported in the larger animals by I,eblanc and Tscheulin, 

 and in dogs and ducks by Hilbert. 



Much more frequently the determining lesions are situated in 

 the brain or its meninges. In sheep it is very common from the 

 development of ccenurus cerebralis over the optic lobes. Kiihnert 

 found a cyst with delicate walls in the brain of a horse affected 

 in this way. Amaurosis is occasionally seen in connection with 

 the cerebral abscesses which form in complicated cases of strangles 

 or in pyaemia, also in cases of cholesteatoma of the choroid 

 plexus. Other conditions of its occurence are hydrocephalus, 

 meningitis, hypertrophy of the pineal gland, fracture of the 

 cranium, tumors of the cranium or dura mater, embolism or 

 aneurism of the cerebral arteries, hypertrophy and induration of 

 the dura mater (ox, Leblanc) , or sanguineous apoplexy. In a 

 certain number of cases there may be no lesion of brain or eye, 

 or only a congestion of the former in connection with lead 

 poisoning, rye grass poisoning or other gastric disorder, or of 

 gestation. 



Treatment. Success will depend on the sympathetic nature of 

 the condition or on the transient and removable character of its 

 causative factor. When the condition is but a symptom of over- 

 loaded stomach or a transient poisoning by vegetable or mineral 

 agents a direct recovery may be expected to follow their disuse 

 and elimination from the system. This may be hastened by the 

 exhibition of laxatives and diuretics, and in the case of lead by 

 sulphuric acid followed by iodide of potassium. In cases of snow 

 blindness it is only necessary as a rule to place the animal in the 

 shade until the over-stimulation shall have subsided. In all 

 these cases the attack has come on abruptly and without any 

 local symptom of ocular hypersemia and this with the preserva- 



