416 Veterinary-Captain F. Smith. [Apr. 26, 



horses commonly exhibit themselves by " shying," a vice which may 

 be attended by considerable danger. I shall hope to show that there 

 is now a reasonable prospect of determining the cause of " shying " 

 in the absence of pathological changes in the eye ; further, that in 

 that important branch of the veterinary art the examination of 

 horses for soundness it should be possible to detect the kind of eye 

 against which an intending purchaser should obtain a special 

 warranty ; and, lastly, as it is possible not only to determine the 

 nature of the refraction, but also the amount of error which exists, 

 we shall be able when the needful public prejudice is overcome 

 to prescribe glasses for horses with every reasonable prospect of i 

 proving their vision. 



This is not the first time the refraction of the horse's eye has been 

 examined. Professor Berlin, of Stuttgart, published two papers e: 

 the subject,* of these I have only been able to consult the 

 one. About the same time J. Hirschberg published his observa' 

 on the refraction of horses' eyes.f 



In this country Messrs. Lang and Barrett, to whose paper I 

 already alluded, published an account of the refraction of the eyes 

 animals, including the horse. It is from their paper that I obtained 

 two of the above references. 



These observers obtained results which I have not been able 

 verify, and I think the reason of this admits of easy explanation 

 In the case of Berlin the refraction was obtained by a di 

 examination of the fundus of the eye with the ophthalmosco 

 procedure the result of which appears to depend very largely on 

 ref faction of the examiner, and his capacity for relaxing his ac 

 modation. 



In Lang and Barrett's excellent work the refraction was meas 

 by means of " retinoscopy." They devoted their attention to the 

 of mammalia generally, but the number of horses tested by t 

 was too small to admit of any general deductions being drawn. 



According to Berlin, the majority of horses are slightly h 

 metropic ; he only met with eight cases of myopia in as many y 

 The amount of hypermetropia, according to this observer, is small, 

 a rule, lying between 1 D and 2 D. The largest amount found 

 him was 2'25 D. 



* " Refraction und Refractions- Anomalien von Thieraugen," ' Tagblatt der 

 Versammlung Deutscher Naturforscher und Aertze in Baden-Baden,' p. 31 

 (Extract in ' Nagel's Jahres-Bericht.') 



" Ueber den Physikalisch-optischen Bau des Pferdeauges," ' Zeitschrift 

 vergleichende Augenheilkunde," 1882, Heft I. 



t " Zur vergleichenden Ophthalmoscopie," Yortrag gehalten in der Ber 

 Physiologischen G-esellschaft am 10 Feb., 1882; ' Archiv f. Anat. und Pliya.,' 18 

 ' Phys. Abth.,' Heft 1 and 2, p. 81. 



