ABDOMINAL MUSCLES. 325 



backwards to the spine, it would have hindered their motion, 

 which is greatest in the middle, though the obliquity of the 

 ribs renders it less perceptible ; and, instead of raising the fibres 

 fixed to the sternum and spine, would have depressed the ribs. 



N. B. The portions of the external intercostals, which arise 

 from the transverse processes of the vertebras where the ribs 

 are fixed to them, and other portions that pass over one rib 

 and terminate in the next below it, Albinus calls Levatores 

 costarum longiores et breviores. 



The portions of the internal that pass over one rib, and are 

 inserted into the next below it, are, by Douglas, called 

 Costarum depressorcs proprii Coivperi. 



These portions of both rows assist in raising the ribs in the 

 same manner as the rest of the intercostals. 



The muscles within the thorax form one pair, viz. 



Triangularis, or Sterno-Costalis, 



Arises, fleshy, and a little tendinous, from all the length of 

 the cartilago-ensiformis laterally, and from the edge of the 

 lower half of the middle bone of the sternum, from whence its 

 fibres ascend obliquely upwards and outwards. 



Inserted, generally by three triangular terminations, into the 

 lower edge of the cartilages of the third, fourth, and fifth ribs ; 

 near where these join with the ribs. 



Use. To depress these cartilages, and the extremities of the 

 ribs ; and consequently to assist in contracting the cavity of the 

 thorax. 



This muscle often varies ; and is sometimes inserted into the 

 cartilage of the second rib, sometimes into the cartilages of the 

 sixth rib. 



Muscles situated on the anterior part of the Abdomen. 



They consist of three broad layers on each side of the belly 

 and, of one layer in front. 

 The three layers are : 

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