102 On Heterochromia Iridis in Man and Animals 



In some individuals this duplex ray takes the form of a darker 

 pigmented sector or patch on a ground colour of lighter duplex instead 

 of a blue background. 



This radial sector of duplex pattern in an eye of simplex or lighter 

 duplex ground colour, I propose to call the ray pattern of the duplex 

 type. 



Iris Structur'e in Man. 



Although as we shall see later cases of irregular pattern of iris 

 pigmentation also occur in animals and birds, yet the pigmentary 

 deposit is less sharply defined in outline, less sectorial or ray-shaped 

 in them than in man. It is probable that this difference in pigmentary 

 pattern may depend on the very definite radial arrangement of the 

 connective tissue stroma of the iris in the human subject. This frame- 

 work tissue and the muscular fibres which dilate the pupil form a 

 network of radiating fibres with lozenge-shaped interstices which 

 generally converge to form a ring with knot-like intersections at a 

 little distance from the pupillary margin, and it is in the situation of 

 this ring of intersections that the greatest deposit of pigment occurs in 

 the so-called duplex ring pattern. 



This ray-like formation of supporting tissue is well seen in the blue 

 human iris in which there is no obscuring anterior pigment, and even 

 more clearly still in the albinotic iris. 



In the iris of birds and of many animals on the other hand the 

 concentric zone-like disposition of the fibres is more marked and obscures 

 the radial pattern. 



Prevalence of the Ray Pattern in Man. 



Out of 200 consecutive eye-cases attending Dr Henry's clinic there 

 were three examples of this ray type, that is 1^ per cent, of eye cases 

 (not of the general population). Of these one was a brown or duplex 

 ray on a blue or simplex background. Two were dark brown rays on a 

 ground colour of lighter brown and in one of these a few dark pigmentary 

 spots were present in addition to the pigmented ray. 



Through the kindness of Mr Ridley and other medical men and 

 nurses I have examined 40 other cases of the ray pattern in the last 

 six months. 



In 21 of these a well-defined duplex triangular ray or rays existed 

 on a simplex background, the other eye in the same individual being of 

 the simplex type. 



