[mass noun] A purplish-red light-sensitive pigment present in the retinas of humans and many other animal groups.
- ‘And for vision it is also necessary that there should be visual purple behind the retina and an opaque cornea and iris.’
- ‘In 1877, Boll and Kuhne independently published their classical studies on visual purple, the photoreceptor pigment of rods, and established that it was involved in the detection of light.’
- ‘It is the reddish purple color of retinal that gives rhodopsin its former name visual purple.’
- ‘Night vision is impaired when there is a lack of re synthesis of retinal necessary for forming visual purple.’
- ‘The photoreceptor of rod cells is specifically called rhodopsin or visual purple.’
We take a look at several popular, though confusing, punctuation marks.