1.- Nervio óptico
2.- Retina
3- Iris
4.- Cristalino
5.- pupila ​

thats a little if u want the answer just look it up on google thats what i do haha : )

answer; 4 electrons;

alchemy hadn't scientific methods of study, appeal to mysticism and fantasy, the knowledge of chemistry and physics were modest at that time.

alchemy was - but as new rules were discovered it either changed into chemistry or it became "unscientific".