PERIODIC OPHTHALMIA. 93 



Transactions of the Veterinary Medical Association, in The Vete- 

 rinarian for 1840 — inclines to the French opinion: he thinks 

 ophthalmia springs out of the local plethora produced in the head 

 about the fourth year of age by the development of the molar teeth. 



Mr. Castley, strongly as he has expressed himself in favour of 

 hereditary causation, has known ophthalmia to supervene on great 

 exertion, on an extraordinary day's work, and on violent exhaus- 

 tion : he has seen an instance or two of its making its first appear- 

 ance in states of great debility, and inanition from blood-letting. 

 To this, adds Mr. C, '' high feeding, and forcing the anim.al to 

 breathe an impure atmosphere, are without doubt among the com- 

 mon exciting causes of this complaint." Mr. C. had also noted, in 

 the course of practice, several cases which induced him to believe 

 the disease might spring out of a metastasis, or certain disturbed 

 states of the system. He thought he had seen it occur after long 

 continued and repeated attacks of diabetes fpolyuria ?). 



Sudden exposure to Light, after having been long confined 

 in dark situations, has been known to induce the disease. Mr. 

 Dunn, V.S., during his apprenticeship, saw several horses, which 

 had been examined previous to descending into coal pits, and 

 found perfectly sound in their eyes, who, after having been but a 

 short time in the pits, were soon after their emergence attacked with 

 severe ophthalmia, which terminated very rapidly in blindness. 

 This is an observation worth something to us. It is just possible 

 that young horses standing for two-or-three-and-twenty out of the 

 four-and-twenty hours, daily, in dark stables, and on occasions for 

 two or three or more days together, may feel the change in their 

 eyes when brought out of their dark stalls suddenly into thejglare 

 of a meridian sun. 



Professor Coleman's Opinions on this ophthalmia we learn 

 from his Lectures to be, that the disease is never seen prior to the 

 domestication of the animal ; never occurs on a common or in the 

 open air, but is the product of the poison generated from the 

 effluvia of the breath, dung, and urine, of horses standing together. 

 Li proof of which the disease is found to be more or less prevalent 

 according as the stables in which horses stand are more or less 

 confined or ill- ventilated : where there occur most cases of in- 



