216 ENTOZOA FOUND IN MAN. 



within the eyeball, and headache. Loss of vision 

 comes on gradually untD. the sense of sight is at last 

 completely destroyed. The iris sometimes changes 

 its normal colour, but in the majority of cases no 

 apparent alteration of the eye is perceptible ; the 

 other symptoms are similar to those which are pre- 

 sent in all affections of the eye which are accompanied 

 by dimness or loss of vision, and the aid of the 

 ophthalmoscope is necessary in order to determine 

 the existence of a cysticercus. 



By means of this instrument, a small object may 

 be seen, which is generally of a spherical shape, at 

 least when the eye and the entozoon are quiescent, 

 and of a bluish, greenish, or grey colour; its relation, 

 with respect to the retinal vessels, varies according to 

 the position which it occupies. When it is situated 

 immediately in front of the retina, or in the vitreous 

 humour, the retinal vessels do not pass in front of 

 the object, but stop at its circumference, or are 

 altogether invisible ; but when the entozoon is lodged 

 in the substance of the retiiia, or between this struc- 

 ture and those which are more deeply placed, the 

 retinal vessels may be seen to ramify upon the object, 

 or to run across it in order to divide farther on, as in 

 the healthy condition. 



The tumour situated at the bottom of the eye is 

 apparently formed by a cyst, whose delicately thin and 

 transparent wall allows the entozoon to be seen, and 

 its form and movements to be recognized. When the 

 cysticercus is developed behind the retina, this struc- 

 ture is sometimes ulcerated, and the worm escapes 

 into the vitreous humour. In some cases the cysti- 

 cercus perishes, and becomes atrophied ; Graefe men- 



