Larraman's Organ, also called the Healer, is the 5th of the 19 gene-seed organs that are implanted into a Space Marine Neophyte to produce a new Astartes. Shaped like the human liver but only the size of a golf ball, this gene-seed organ is placed within the chest cavity and manufactures the synthetic biological cells known as Larraman Cells that were named after one of the researchers in the Emperor of Mankind's gene-laboratories on Terra where the gene-seed for the first Space Marines was created under the Emperor's direction from his Primarchs' DNA. These biosynthetic cells serve the same physiological purpose for an Astartes as the normal human body's platelets, serving to clot the blood lost from wounds, but they act faster, more efficiently and more effectively. When a Space Marine is wounded and incurs blood loss, Larraman Cells are released by his circulatory system, attached to the body's normal leukocytes (white blood cells). At the site of the injury, they form scar tissue in a matter of seconds, effectively preventing massive blood loss and infection of the wound. The action of this organ is one of the reasons that the Space Marines are seen as nearly invincible and so difficult to kill despite the terrible wounds they sometimes endure.
- Codex: Space Marines (5th Edition)