“The sensory cortex is arranged in a specific pattern forming a corresponding "map" of the body (see the homunculus in Fig. 23-1). Pain in the right hand is perceived at its specific spot on the left cortex map. Some organs are absent from the brain map such as the heart, liver, or spleen. You know you have one but you have no "felt image" of it. Pain originating in these organs is referred because no felt image exists in which to have pain. Pain is felt "by proxy" by another body part that does have a felt image. For example, pain in the heart is referred to the chest, shoulder, and left arm, which were its neighbors in fetal development. Pain originating in the spleen is felt on the top of the left shoulder.”