110 VETERINAEY OPHTHALMOLOGY. 



tissue framework as they traverse the various layers 

 and spread out in its membranes. At the oru serrata 

 all the nerve elements disappear and the connective 

 only continues, forming the zonule of Zinn. 



The Macula lutea,ox yellow spot, is the seat of most 

 acute vision. The macula contains no rods, while the 

 cones are longerand narrower than elsewhere. At the 

 center all the retinal layers are thinned, and this is called 

 thQ fovea ce?itralis. The retina possesses a particular 

 vascular distribution. The arteria centralis retinae 

 with its vein enters the optic nerve at a short distance 

 from the globe, and with it passes into the eye. They 

 traverse the papilla and immediately divide into two 

 branches, one up, the other down. These branches 

 then turn out, but none of its capillaries extend into the 

 fovea* 



Now, though the choroid and retina may be in- 

 dependently inflamed, I propose to describe inflam- 

 mation of both under Internal Ophthalmia. Severe 

 blows, punctures, foreign bodies, sudden transition 

 from, darkness" to brilliancy, glare of snow, cold 

 and dampness, high winds, (front of ferryboats, for 

 instance), rain, exposure when heated, and many 

 general diseases, among which are rheumatism and 

 influenza. Met with during dentition. There are 

 not many external symptoms, unless the cause was 



* The above description of the retina was taken largely from. 

 JKorton's excellent work. 



