THE MUSCLES OF THE SKIN. 95 
This muscle lies immediately beneath the integument. It 
covers the first layer of body muscles. 
Acton. —Moves the skin. 
M. platysma (Figs. 62 and 64, a, a’, a’’).—This muscle 
forms a thin layer of fibres covering the sides of the neck and 
face, in close relation with the integument. Several more or 
less distinct portions may be distinguished. 
(1) Most of the fibres (a) arise from the middorsal line, from 
the occiput to the first thoracic vertebra, in a narrow fascia 
common to the muscles of the two sides. The most cranial 
fibres of this region arise as a small bundle from the external 
occipital crest, beneath’the levator auris longus (Fig. 63, 
& ) 
From this origin in the middle line the fibres pass cranio- 
laterad. The most cranial fibres curve about the ventral side 
of the ear and pass toward the caudal angle of the eye, where 
they unite with fibres of the zygomaticus (Fig. 64, @) or corru- 
gator supercilii lateralis (Fig. 64, %), or pass to the lower 
eyelid. Caudad of these the fibres cover the side of the face 
and become lost among the facial muscles, some passing to the 
lower eyelid, some to the fibrous pad which supports the 
vibrissze, some to the angle of the mouth, some to the lower 
lip. The most ventral fibres meet the fibres of the opposite 
muscle just ventrad of the symphysis of the mandible. 
The ventral free border of the platysma is separated on the 
ventral side of the neck from the border of the opposite muscle 
by a wedge-shaped area having its point at the symphysis 
menti. 
The fibres of this portion of the muscle are interrupted by 
an attachment to the skin, along a line passing from the base 
of the ear to about the middle of the coracoid border of the 
scapula. The dorsal (2) and ventral (@’) portions of the 
muscle, separated by this line of attachment, are sometimes 
described as separate muscles (the supercervicocutaneus and 
cervicofacial, respectively, of Strauss-Durckheim). 
(2) A band of fibres one or two centimeters across (a”) 
arises in the fascia of the side of the neck just craniad of the 
middle of the coracoid border of the scapula, and passes caudo- 
