FUNGUS HiEMATODES. 555 



they also must be removed. If the patient be a cow, ox, or sheep, 

 and if in fair condition, it should be slaughtered, as the tumour 

 tends to return even if removed early, and death is apt to occur 

 from marasmus, pain, and hsemorrhage. 



PERIODIC OPHTHALMIA. 



Periodic ophthalmia is now rarely met with. Fifty years 

 ago thousands of horses became annually blind from ophthalmia ; 

 now-a-days one seldom sees a case of blindness from this 

 cause. This happy result is due to the enlightened writings 

 of Coleman on ventilation, and to the advance of veterinary 

 science — facts which the public seem to ignore. 



It has been variously termed " specific ophthalmia," " periodic 

 ophthalmia," or " moon-blindness." 



The term " periodic ophthalmia," is here retained, as it implies 

 the recurrent or intermittent character of the disease; but it 

 throws no light upon the pathology. 



Periodic ophthalmia is a constitutional affection — cachectic or 

 diathetic, probably rheumatic — arising from some cause opera- 

 ting primarily on the constitution, and secondarily on the organ 

 of vision, terminating in an opacity of the crystalline lens, 

 termed cataract. 



Symptoms. — The attack generally comes on suddenly, without 

 ostensible cause, and in the night. The eye presents signs of 

 weakness, the upper lid droops, the eye seems smaller than 

 its fellow, it is drawn into the orbit by the retractor muscle ; 

 removed, as it were, as far as possible from the light, which, 

 from its sensitiveness, it cannot bear: intolerance to light is 

 also manifested by repeated rapid nictitations, and by recoil of 

 the globe within the orbit. This is especially evinced when a 

 strong light is suddenly brought to bear on the eye — and it is 

 further protected by the drooping of the lids, its natural curtain ; 

 the membrana nictitans projects ; the tears flow over the lower 

 lid and bedew the face. When the eye is more closely in- 

 spected, the cornea is dull; the dulness, at first most intense at 

 its margin, but soon spreading over its surface, rendering a view 

 of the interior structure of the eye an impossibility. The 

 dulness is inclined to an amber colour ; and it was maintained 

 by Professor Dick that this was due to the fulness and pressure 



