THE MUSCLES 95 



separated by a wide median aponeurosis, or linea alba. The muscle 

 may be regarded as extending from the anterior edge of the pubis 

 to the level of the sternal cartilage, and is interrupted by ten tn- 

 scriptiones tendineae — not counting the terminal inscription lateral 

 to the sternum. It is, therefore, difficult to speak of 'origin' and 'in- 

 sertion', since each inscription is firmly attached to the overlying 

 skin. The direction of the fibres is longitudinal. The muscle is 

 fairly easily separable into two portions, namely, a thicker mesial 

 and a thinner lateral section, while the epigastric arteries run along 

 the line of junction between them. Anteriorly the fibres take several 

 courses, the most lateral merge into the M. pectoralis, the most 

 mesial fibres pass dorsal to this muscle and are inserted on the 

 postero-lateral edge of the sternal plate, and on the pericardium, 

 while the remainder of the muscle continues directly forwards, 

 dorsal to the coracoids, as the M. rectus cervicis superficialis (q.v.), 

 and is inserted on the hyo-branchial apparatus. In addition to its 

 attachment to the pubis a few of the posterior fibres are inserted on 

 the lateral processes of the ypsiloid cartilage. 



M, rectus abdominis prof undus (m.r.ab."). Maurer (i 892). 

 This muscle also extends from the pelvis to the hyoid, but unlike the 

 superficial portion it lies more or less free throughout nearly its whole 

 length. It arises from the anterior edge of the pubes deep to the 

 superficial stratum, and is also interrupted by tendinous inscriptions 

 of which only one or two of the most caudal are attached to those of 

 the M. rect. abd. super., the remainder being entirely free. Anteriorly 

 the muscle becomes rather more lateral in position and the inscrip- 

 tions fail to correspond exactly with those of the other muscles, and 

 also tend to become less distinct. This is doubtless to be explained 

 by supposing that the freedom of the muscle has allowed a certain 

 amount of stretching of the myomeres to occur. 



The portion of the muscle anterior to the sternum forms the M. 

 rectus cervicis profundus (q.v.) 



Innervation: Both sections are innervated by the terminal 

 branches of the spinal nerves 5-15 inclusive. 



Function : In general they serve to flex the vertebral column, while 

 they also act on the hyo-branchial apparatus and tend to compress 

 the viscera. 



M. ypsiloideus anterior. Whipple (1906). 



Consisting of only a few fibres which take their origin from the 



anterior edge of the lateral processes of the ypsiloid cartilage^ and 



