62 MUSCLES OF THE THORAX. 
band and reflect the cut ends; the remaining divisions 
of the pectoralis will be fully exposed. The fibres | 
arise along the whole length of the sternum, pass 
obliquely forward and outward to be inserted into the 
head and upper part of the shaft of the humerus, and 
partly also into the fascia covering the biceps muscle 
of the arm. 
Cut across the pectoralis muscle and reflect the cut 
ends. 
2. The Sternalis Muscle is a small fan-shaped mus- 
cle lying lateral to the anterior end of the sternum. 
The muscular fibres arise at the level of the cartilagi- 
nous portion of the 2d and 3d ribs from a strong 
fascia ; they pass obliquely forward and outward to be 
inserted into the rst rib. 
3. @he, scalent Muscles arise, iromy the=transverse 
processes of the last four cervical vertebrae, and are 
inserted into the ribs. In the dog four scaleni may 
be distinguished lying close to one another : 
a. THE SCALENUS Primus lies nearest to the ven- 
tral mid-line; it arises from the transverse processes 
of the 5th and 6th cervical vertebrz, and is inserted 
into the 1st rib where the bony and cartilaginous por- 
tions meet. 
b. THE ScaLEnus SEcuNDUS is much longer; it 
arises from the transverse processes of the 4th and 5th 
cervical vertebree by two tendons, and is inserted into 
the bony ribs from the 3d to the 7th. 
c. THe ScaLenus Tertius lies dorsal to the ante- 
rior end of the secundus; it arises in common with it, 
but is inserted into the bony portion of the rst rib to 
the outer side of the insertion of the primus. 
d. THE ScaLENUS QuARTUS is a very small muscle 
inserted into the 1st rib between the primus and 
