/ESTHESIOLOGY 

 THE SENSE ORGANS AND COMMON INTEGUMENT 



The organs of the senses (Organa sensuum) receive external stimuli and conduct 

 impulses to the l^rain wiiich result in sensations of sight, hearing, taste, smell, and 

 touch. They consist essentially of specially differentiated cells, the neuro-epithe- 

 lium, and a conduction path which is simple in the more generalized sense organs, 

 elaborate in those which are highly specialized — the eye and the ear. 



THE SENSE ORGANS AND SKIN OF THE HORSE 

 The Eye 



The eye or organ of vision (Organon visus) in the broader sense of the term 

 comprises the eyeball or globe of the eye, the optic nerve, and certain accessory 



Upper eyelid 

 Third eyelid ; 

 Caruncula \ > 



lacrimalis 



Inner cariihus 



Lower eyelid 

 Fig. .551.- I,i;i-r Kyk of Horsk. 

 9, ZyKomaiic arch; W, .supraorbital depression; 12, supraorbital process; Z7, facial crest. (After EUenberger- 



Baum, Anat. fiir Kiiustler.) 



organs associated liierewith. The accessory organs (Organa oculi accessoria) are 

 the orbital fascia and muscles, the eyelids and conjunctiva, and the lacrimal 

 apparatus. These structures will be considered in the order in which they may be 

 most conveniently examiiKul, taking th(> horse as a type. The bony walls of the 

 orbit have been descril)ed in conncH-tion with the skull; the periorbita, a fibrous 

 membrane which incloses the eyeball together with its muscles, vessels, and nerves, 

 may be appropriately included in the account of the fascia?. 



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