ELEMENTf< OF HIPPOLOGY. 53 



Blindness is common among horses. If it results from an 

 injury to the external eye or from cataract, it is easy of discovery; 

 if from disease in, or destruction of, the optic nerve, it is not 

 so apparent. 



A cataract shows itself as a milky opacity in the interior 

 of the eye. Its seat is in the crystalline lens or its coverings. 

 What is known as the candle test is the surest method of de- 

 termining whether an opacity in the eye is or is not a cataract. 

 In a partially lighted place a lighted candle is held in front of the 

 eye. If the eye is perfect, three images will be seen — one, the 

 front one, erect, is the reflection from the , outer surface of the 

 cornea; the second, also erect, is the reflection from the front 

 surface of the crystalline lens; the third, inverted, is the reflection 

 from the back of the lens. As the candle is raised or lowered, the 

 first and second images go up or down, the third moves in a con- 

 trary direction. If a cataract is present, the inverted image is 

 blurred, or wanting altogether; if the trouble -is in front of the 

 lens, there will be but one distinct image. 



A good preliminary test for blindness is to raise the hand 

 from below to the level of the eye and near it, then to withdraw 

 it, but not so rapidly as to cause appreciable air-currents. If 

 the horse does not wink or dodge, there is grave suspicion cast 

 at once on his vision in that eye. 



In order to give lightness to the head, and at the same time 

 to afford room for the attachment of the various muscles of mas- 

 tication, some of the bones of the horse's face are hollowed out, 

 leaving blind cavities, opening only downward. These cavities 

 are called the facial sinuses, and seem to have no function, 

 except that mentioned. 



The neck includes seven of the vertebrae of the spinal 

 column. The muscle that moves the foreleg forward is attached 

 to the head and the first four of the neck vertebrae; the longer this 

 muscle is, the greater will be its contractibility and consequent 

 leverage on the bones of the foreleg and the stronger will be the 

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