574 Froceedings of the Royal Society 
portion of the retina of his right eye, though the vision of the eye 
was perfect, was actually blind or insensible to visual impressions, 
while it was so sensible to luminous impressions, that no spot of 
the slightest darkness or shade was seen in the field of vision when 
directed to the sky or any extended white surface. When the 
image of a bright object, or of the setting sun, was received on 
this portion of the retina, which was about the twenty-eighth part 
of an inch in breadth, it was wholly invisible, and therefore the 
light with which it was impressed must have been derived by irra- 
diation from the adjacent parts of the retina, or from those parts of 
it which underlie the insensible part. Hut for this property the 
patient would constantly see a black spot disfiguring the aspects 
of nature, and ever reminding him of his misfortune. 
The author mentioned a temporary affection of the same eye, 
observed thirty years ago, on which two lines, radiating from the 
foramen centrale, were absolutely black. 
3. On some Laws of the Sterility of Women. By 
J. Matthews Duncan, M.D. 
In this paper absolute sterility is held to mean the condition of 
a woman who, under ordinary favourable circumstances for breed- 
ing, produces no living or dead child, nor any kind of abortion. 
Sterility is held to mean the condition of a woman who, under or- 
dinary favourable circumstances for breeding, produces no living 
and viable child, or adds not one to the population. Eelative 
sterility is held to mean the condition of a woman who, while she 
may or may not be absolutely sterile, while she may or may not be 
sterile, is, under ordinary favourable conditions for breeding, sterile 
in relation to the circumstance of time, or, in other words, in re- 
lation to her age and the duration of her married life. 
The sterility of marriages in our population is estimated as 19 
per cent. 
The sterility of wives, married at ages from 15 to 44 inclusive, 
is shown to be 15 per cent, or about 1 in 6|. 
The absolute sterility of wives may be held to approximate 
closely to the sterility of wives ; for to the data used in calculating 
the sterility of wives there would only have to be added the wives 
