The =musculo-cutaneous nerve= (Fig. 441) arises close behind the
suprascapular, and is derived chiefly from the part of the brachial
plexus which is supplied by the seventh and eighth cervical nerves. It
descends across the outer surface of the brachial artery, below which a
great part of the nerve unites with the median to form the loop
previously mentioned. It gives off a branch which enters the upper part
of the belly of the coraco-brachialis, passes downward and forward
between the two parts of that muscle or between the muscle and the bone,
and divides into branches which enter the biceps brachii. It contributes
one of the nerves to the pectoral muscles. In some cases this nerve
sends a branch to join the cutaneous branch of the median.