MUSCLES OF THE THORAX MUSCLES OF THE BACK AND LOINS 313 



portion (Biventer cervicis) is marked by several tendinous intersections; the 

 ventral part is the complexiis proper. 



The obliquus capitis posterior is relatively thin. 



The recti capitis are thick and more or less fused. 



MUSCLES OF THE THORAX 



The levatores costarum and rectus thoracis present no special features. 



The external intercostal muscles are absent under the serratus anticus and 

 posticus and the diiiitations of the external oblique. 



The internal intercostals are thick between the cartilages of the sternal ribs. 



The retractor costae and the transversus thoracis resemble those of the horse; 

 the latter extends back to the eighth cartilage and fuses with the transversus 

 abdominis. 



The diaphragm has seven costal digitations on each side, the posterior ones 

 being attached to the ribs at some distance (ca. one-third to one-fourth of rib- 

 length) from the costo-chondral junction. The line of attachment reaches the 

 latter at the tenth rib, and passes along the eighth cartilage to the xiphoid process. 

 The tendinous center is more rounded than in the horse. The crura are well 

 developed. The right crus is very large, and is perforated by the extensive slit- 

 like opening for the oesophagus, which is median in position, and lies about two and 

 one-half to three inches (ca. 6 to 8 cm.) below the twelfth thoracic vertebra. The 

 hiatus aorticus is between the crura. 



Abdominal Muscles 



The abdominal tunic is little developed. 



The obliquus abdominis externus has an extensive fleshy portion and a cor- 

 respondingly narrow aponeurosis; the latter does not detach a femoral lamina, 

 but is reflected in toto to form the inguinal (Poupart's) ligament. 



The obliquus abdominis internus resemblessthat of the ox; a small fusiform 

 muscle, which crosses the inguinal canal obliquely and is attached on the abdominal 

 surface of the inguinal ligament, is apparently a detached slip of the internal 

 oblique. 



The rectus abdominis is extensive and thick. It has seven to ten intersections. 

 Its tendon of insertion fuses largely with the common tendon of the gracilis, and 

 does not give off an accessory band to the head of the femur. 



The fleshy part of the transversus abdominis is well developed. It blends in 

 front with the transversus thoracis. 



The cremaster externus is present in the female as well as in the male. 



Muscles of the Back and Loins 



The serratus anticus is inserted into the fifth to the eighth ribs inclusive, the 

 serratus posticus into the last four or five ribs. There are usually no digitations 

 attached to the ninth and tenth ribs. 



The transversalis costarum (Iliocostalis) extends to the wing of the atlas. 



The spinaUs et semispinalis can be separated without much difficulty from the 

 longissimus dorsi, the division from the common mass of the loins beginning about 

 the first lumbar vertebra. 



The multifidus resembles that of the horse. 



Interspinales are present, as well as distinct intertransver sales of the back 

 and loins. 



