Tapetum lucidum
As a tapetum lucidum cellulosum, tapetum lucidum short (Latin for " bright carpet " ), even shorter tapetum is a reflective layer called that, behind or in the middle of the retina of the eye of many nocturnal animals (eg cats and dogs ) but also cattle and horses is. It is formed postnatally.
The incident light passes through the retina and is reflected to this layer, and passes through the retina for a second time.
Depending on the species are zinc -cysteine, salts, pigments or - in some insects - filled with air Tracheenästchen or crystalline deposits - as with the spiders - responsible for the reflection.