AMMON ON THE SPOT OF SOEMMERING. 433 



tion, made upon the eye of a convict within three hours 

 after execution. In this case the yellow spot of Soemmering 

 was very manifest, and about two lines in diameter ; buj/ the 

 surface of the retina was perfectly plain, and the foramen 

 appeared to be but a superficial depression, the size of a small 

 pin's head, with a slightly elevated brilliant yellow margin. 

 Dalrymple observed in one case the surface of the retina, per- 

 fectly smooth, and as the fluid escaped, the circular edges of 

 the cup-like depression, (which he with Meckel and others, 

 consider the foramen of Soemmering merely to be,) were elon- 

 gated, elevated, and finally came in contact, forming the fold of 

 Soemmering. 



According to Ammon, who has written a work, ex-prof e$so 

 upon the yellow spot of Soemmering, there is never at any 

 period of life to be found the foramen of which this author 

 speaks. The depression on the surface of the retina, and the 

 appearance of a foramen are owing to the more intimate union 

 at this point, of the choroid and retina by the intermedium of 

 vessels. The yellow spot, limbus luteus according to him, 

 is very vascular, and is usually apparent fourteen or fifteen 

 months after birth, and is always to be found in the healthy 

 adult eye. He has twice sought for it in vain, in cases of 

 amaurosis, and once in congenital cataract. In the early pe- 

 riods of fostal life, the choroid is red, and contains no black 

 pigment. 



After the pigment is deposited, and toward the period of 

 birth, its color in the axis of the eye, where the yellow spot 

 is to appear, is of a lighter brown than in other parts. As the 

 spot begins to make its appearance fourteen or fifteen months 

 after birth, the yellowness is first obvious on the outer side of 

 the retina, next to the choroid, and he believes is entirely de- 

 pendent on the action of light upon the retinal surface of the 

 choroid pigment. 



The pigment, diluted with water, and exposed to the action 

 of the rays of the sun, he says assumed a yellowish appearance. 

 VOL. ii. 37 



