548 DISEASES OF THE EYES. 



made, I have found that the vitreous humour has heen converted 

 into a semi-cartilaginous or even calcareous mass, and that 

 instead of fluidity there was solidification of the humour and 

 its membrane. The glaucoma of old age may occur without 

 previous inflammation, and in dogs it most commonly occurs 

 in tliis way ; but in horses I have always found it associated 

 with some traces of previous ophthalmia. The term hlue can 

 scarcely be applied to the lower animals, green or bluish-green 

 being more significant. Melanosis of the humours has been 

 observed. 



DISEASES OF THE NERVES OF THE EYE. 



Amaurosis, as a disease of the eye sui generis, is a condition 

 of the optic nerve and its expansion — the retina — ^whereby 

 they lose the power of receiving and transmitting the impres- 

 sions of objects to the great nervous centre, the brain. 

 Amaurosis as a disease of the optic nerve is incurable, but the 

 condition often exists as a symptom of other diseases, more 

 particularly of organic and other lesions of the brain, the effects 

 of various vegetable and animal poisons, and of excessive 

 haemorrhage ; but it is not my purpose to discuss these at the 

 present time. 



Amaurosis, gutta serena, or glass eye, in the horse presents 

 the following symptoms : — A preternaturally dilated, round, 

 and motionless pupil ; the eye lucid or glassy in aspect ; the 

 eyelids opened more than natural — ^in fact, the animal may be 

 said to stare. The gait and the motion of the ears are indica- 

 tive of blindness. 



It is possible to have amaurosis in one eye, but this is very 

 rare in the lower animals, and is generally indicative of brain 

 disease. Amaurosis with cataract is a common termination of 

 constitutional ophthalmia. Excessive haemorrhage has produced 

 sudden but permanent amaurosis, both in the horse and cow. 

 Can it be that, in such instances, the paralysis is due to the 

 failure of the circulation in the arteria centralis retinae ? In 

 the human subject, " amaurosis is sometimes due to exhaustion 

 of the optic nervous apparatus, and is often a mere accom- 

 paniment of general nervous exhaustion, arising from great loss 

 of blood, or excessive discharge of secretions," &c. — (Wharton 

 Jones.) 



