50 THE HEAD AND NECK. 



the purchaser will reject or receive a horse par- 

 tially or totally blind. 



Gutta Serena, or Glass Eyes, is a disease in 

 which the horse is quite blind, without any ap- 

 parent alteration in the structure of the eye. 

 The optic nerve is palsied, and insensible to the 

 rays of light. When it exists in both eyes, the 

 general appearance of the horse will at once 

 point out his lamentable condition — the rapid 

 motion of the ears — the high, yet cautious action 

 of the forelegs — and the extreme readiness with 

 which the animal yields to the least movement 

 of the bit. 



When only one eye is affected with Gutta serena^ 

 it may be discovered by observing what is called 

 the pupil — the opening in the centre of the dark- 

 coloured part of the eyes. It will be found to 

 be considerably larger than the opening in the 

 living eye, and that opening does not contract 

 when the eye is opposed to a strong light. 

 In the other it does, and its contraction and 

 delatation is sufficient evidence of the optic nerve 

 being in health. 



Gutta Serena is unsoundness ; but as It may 

 have come on in an instant, and consequently it 



