290 



MUSCLES AND FASCIAE. 



ference of the thorax, being attached, in front, by fleshy fibres to the ensiform car- 

 tilage ; on each side, to the inner surface of the cartilages and bony portions of 

 the six or seven inferior ribs, interdigitating with the Transversalis ; and behind, 

 to two aponeurotic arches, named the ligamentum arcuaturn externum and liga- 

 mentum arcuatum. internum ; and to the lumbar vertebra. The fibres from these 

 sources vary in length ; those arising from the ensiform appendix are very short 

 and occasionally aponeurotic ; but those from the ligamenta arcuata, and more 

 especially those from the ribs at the side of the chest, are the longest, describe 

 well-marked curves as they ascend, and finally converge, to be inserted into the 

 circumference of the central tendon. Between the sides of the muscular slip 

 from the ensiform appendix and the cartilages of the adjoining ribs, the fibres 



Fig. 107. The Diaphragm. Under Surface. 

 6r.CarKfag* 



of the Diaphragm are deficient, the interval being filled by areolar tissue, covered 

 on the thoracic side by the pleura? ; on the abdominal, by the peritoneum. This 

 is, consequently, a weak point, and a portion of the contents of the abdomen 

 may protrude into the chest, forming phrenic or diaphragmatic hernia, or a 

 collection of pus in the mediastinum may descend through it, so as to point at the 

 epigastrium. 



The ligamentum arcuatum internum is a tendinous arch, thrown across the 

 upper part of the Psoas magnus muscle, on each side of the spine. It is connected, 

 by one end, to the outer side of the body of the first, and occasionally the second, 

 lumbar vertebra, being continuous with the outer side of the tendon of the cor- 

 responding crus; and, by the other end, to the front of the transverse process of 

 the second lumbar vertebra. 



