PHYSIOLOGY, AND PATHOLOGY OF THE CHIMPANZEE. 343 



orii.in of the rectus capitis lateralis, and the latter is the only 

 muscle whose fibres run in the same direction *. 



The multifichis spince extends from the sacrum to the axis. It 

 arises from the sacrum, sacro-iliac ligament, mammillary pio- 

 cesses of the lumbar vertebrse, transvei'se processes of all dorsal 

 vertebrae, and lower four cervical articular processes. It is 

 inserted into the spines of all vertebrae except the atlas. The 

 semispinalis covers it but its fibres, which run in the same 

 direction, are longer than those of the multifidus, and extend 

 to vertebrae farther apart. The cervical fibres of the multifidus 

 do not form broad bands. 



The ohliquus inferior (I.O.M) and ohliquus superior (S.O.M) 

 (text-fig. 34 B) are as in Man. 



The rectus capitis posticus major (text-fig. 34, R.C.P.M) is a 

 powerful pyramidal muscle quite concealing the minor muscle. 

 It arises from the spinous process of the axis and is inserted into 

 the occiput below the entire length of the superior oblique. The 

 rectus capitis posticus minor arises from the inner three-quarters 

 of an inch of the posterior ai^ch of the atlas and is inserted into 

 the occipital bone below the major muscle. It is quite concealed 

 by the latter, and by the approximation of the walls of the sub- 

 occipital triangle. Rectus capitis lateralis is as in Man. 



Interspinales, intertransversarii and levatores costaium are as 

 in Man. Rotatores dorsi are twelve pairs of fan-shaped muscles 

 running from the transverse processes of the dorsal vertebrae to 

 the laminae of the vertebrae above them, the first one being in- 

 serted into the seventh cervical lamina. 



Muscles of the Thoracic Parietes. 



The exter^ial intercostal muscles run in the same direction as 

 those in Man. They extend from the angles of the ribs to the 

 sternum in the first three and last two spaces. But there are 

 external intercostal membra,nes in the other spaces. The internal 

 intercostals do not differ materially from those in Man. The 

 triangularis sierui arises as in Man from the back of the ensiform 

 cartilage, a,nd it is inserted by radiating slips into the sternal 

 ends of the second, third, fourth, fifth, and sixth ribs. It has 

 a slightly different relation to the internal mammary ai'tery from 

 that in Man, the details being given with that vessel on page 386. 



The sternalis muscle is absent. Some authors describe it, and 

 their observations have been collected by Keith (29). 



Contrary to the conditions in Man, there is a well-marked 

 lateral branch of the first intercostal nerve. It runs over the 

 pectoralis major and fades away among the glands in the axilla. 



Prevertebral Muscles. 



The longus colli consists, as in Man, of vertical, superior, oblique 

 and inferior oblique portions. The vertical part arises from the 



* This is probably an individual peculiarity. 



23* 



