MUSCLES OF THE BODY. 15! 
(Fig. 68, f), latissimus dorsi (Fig. 68, w), serratus posterior 
inferior (Fig. 73, 2) and superior (Fig. 73, 7), serratus anterior 
(Fig. 73, 2), scalenus (Fig. 73, 7), and iliocostal (Fig. 69, 2). 
Inner surface with the internal intercostals (Fig. 69, £). 
Acton. —Protractors of the ribs. 
Mm. intercostales interni (Fig. 69, #).—The internal 
intercostals are similar to the external intercostals, beneath 
which they lie. Their fibres pass between the ribs at nearly 
right angles to those of the external intercostals and have nearly 
the direction of the fibres of the internal oblique. They occupy 
all the intercostal spaces from the first to the thirteenth ribs. 
Relations.—Outer surface with the external intercostals 
(Fig. 69, z), and ventrad with the scalenus (Fig. 73, /), trans- 
versus costarum (Fig. 73, 7), and rectus abdominis (Fig. 
73, &). Inner surface with the pleura and the transversus 
thoracis. 
Action.—Retractors of the ribs. 
M. transversus thoracis (triangularis sterni; sternocostalis 
internus).—This represents a thoracic portion of the transversus 
abdominis. It consists of five or six flat muscular bands lying 
on the inner surface of the thoracic wall. 
Origin on the lateral borders of the dorsal face of the 
sternum, opposite the attachments of the cartilages of the third 
to the eighth ribs. The six bands thus formed, each about one 
centimeter wide, pass laterad and are zserted into the cartilages. 
of the ribs near their junction with the ribs, and into the fascia 
which covers the inner surface of the internal intercostals in this 
region. 
Relations. —Outer surface with the internal intercostals and 
the cartilages of the ribs. Inner surface with the pleura. 
Diaphragma (Fig. 74).—The diaphragm consists of a cen- 
tral so-called semilunar tendon (e) and of muscular fibres which 
pass radially from the body wall to the tendon. It forms a 
complete oblique partition between the abdominal and thoracic 
cavities. The dorsal end is farther caudad than the ventral. 
The central tendon (e) is thin and irregularly crescent- 
shaped, with the convexity ventrad and the horns of the cres- 
cent prolonged as two tendinous bands (¢’) which end in two 
