Why was this necessary during WWII?

Blood transfusion was used during WWII to cure soldiers of excessive blood loss. Injured soldiers were treated with albumin. Albumin is a family globular protein, which is commonly a dried egg white. People also used blood plasma to heal.

Blood plasma is a substance that is about 55% of humans body weight. It is a component of blood that holds in the blood cells in the blood, in suspension. It is has a faded yellow coloring.

http://upload.wikimedia.org/wikipedia/commons/1/11/Blood-centrifugation-scheme.png