In the dissection of a frog, why are the arteries red and veins blue?
Generally, when specimens are preserved for science labs, they are usually treated with formaldehyde and glycol to help them resist decomposition. Besides that, for the study of anatomy, they are usually injected with red latex, to clearly show arteries and injected with blue latex, to show the veins. When an organism is alive, the blood in the arteries is bright red and in the veins, dull red. However, the blood vessels are actually a white color when there is no blood in them. Therefore, by injecting the specimen's blood vessels with colored latex, arteries and veins can be easily visualized.