This is in contrast to the subclavian vein, which travels anterior to the scalenus anterior. Sometimes the subclavian vein passes with the artery behind the Scalenus anterior. Sibson muscular part is originated from scalenus minimus muscle. It projects outward medially and is the site of insertion for scalenus anterior. The phrenic nerve is then isolated under the scalenus anticus muscle. It is bounded in front by the scalenus medius and behind by splenius cervicis. Occasionally, it perforates the Scalenus anterior; more rarely it passes in front of that muscle. Scalenus is an Old World genus of round-necked longhorn beetles of the subfamily Cerambycinae.