522 
M. H. REYNOLDS. 
muscles. It is in relation outwardly with tendinous and 
aponeurotic portions of the small complexus, the splenius and 
mastoido-humeralis muscles. Its fibres run forward and 
upward. They originate on the transverse process of the 
atlas and terminate at the mastoid crest and on styloid process 
and external surface of the occipital bone. Its office is to 
produce a slight lateral flexion of the head on the atlas. This 
muscle has the same source of blood supply as the great 
oblique ; but its nerve is the first cervical instead of second. 
The small posterior straight is a little, triangular, flattened 
muscle which lies just over the occipito-atloid articulation. 
Its under surface covers the fibrous capsulo of this articula¬ 
tion. The outer surface related to the great posterior 
straight muscle, which is prismatic, and consists of two por¬ 
tions. It rests below on the preceding and relates to the 
great complexus and oblique muscles. Both straight muscles 
have their insertion on the occipital bone, behind the superior 
* insertion of the great complexus. The larger has its origin 
on the superior spinous process of the axis and the smaller on 
the superior face of the atlas. Their fibres run forward and 
upward. Blood is supplied through the occipital and verte¬ 
bral arteries. Nerves, first cervical and branch from deep 
cervical plexus. The duty of these muscles is to extend the 
head 
/ 
The great and small anterior straight muscles, and the 
lateral straight muscle will be omitted to spare your patience ; 
and the mastoido-humeralis briefly discussed, in conclusion, 
because of its functional importance and frequent involve¬ 
ment in poll evil cases. This muscle is composed of two por¬ 
tions, distinct in origin, but having a common insertion. The 
anterior, and most superficial portion, has its origin on the 
mastoid crest and process of the temporal bone. The pos¬ 
terior takes its origin from the transverse processes of first 
four cervical vertebras and unites with the anterior in forming 
a cap over the scapulo-humeral articulation. The common 
tendon, or rather aponeurosis, inserts on the anterior border 
of the humeral furrow of torsion, just beneath the deltoid 
imprint. This muscle runs obliquely across the cervical 
