ENCEPHALOCELES AND OTHER ABNORMALITIES. 101 



side this bundle is shown somewhat diagrammatieally in figure 21 and labeled 

 sacrospinalis. In the lumbar region it is cylindrical and measures 1.5 cm. in diam- 

 eter. It grows flatter and broader as it nears the upper part of the spine, this 

 formation being due to a state of arrested development of the sacrospinalis and 

 short back-muscles. The early condition of dorsal musculature which it simulates 

 is strikingly illustrated in Bardeen and Lewis's model of an 11 mm. embryo (1901), 

 where a bundle distinct from the ventral-lateral muscles lies bilaterally in the trough 

 formed at the sides of the vertebrae. In another model given in the same paper of 

 a 20 mm. embryo, the bundle may still be seen lying under the connective tissue of 

 the region, and this divided condition of the back-muscles persists normally until 

 about the 60 mm. stage. 



The serati posterior inferior are shown by projections from the dorsal bundle 

 which on both sides cover the proximal half of the three lowest ribs. In the upper 

 thoracic region, lying on the surf ace of the bundle on each side, is a thin strip of muscle 

 near the base of the ribs. These strips extend cranio-cauclally and measure 20 by .'> 

 mm. On the left the strip lies over the third to eighth rib ; on the right side it extends 

 over the first to the sixth rib. The serati posterior superior are not identifiable. 



The direction of the muscles of the anterior cervical region, as well as of those 

 attached to the skull, is distorted with the underlying skeleton, but the muscles 

 are well developed and not defective. Both sterno-cleido-mastoid muscles have 

 normal origins and insertions. The two splenii arise bilaterally from fascia 

 under the scapulae and are inserted normally on the mastoid process under the 

 sterno-cleido-mastoid, and posterior to this on the occipital bone. The longissimi 

 can be traced arising from the fascia over the cervical vertebral region and inserted 

 on the mastoid processes. The semi-spinalis capitis muscles, arising from the upper 

 ribs near their origin, are inserted on the occipital bone and are next to the deepest 

 layer of musculature. The latter on each side consists of short fibers, rudiments 

 of the short neck-muscles, the recti, and obliqui. More anteriorly most of the neck 

 muscles are recognizable. The digaster, stylohyoid, omohyoid, and sternohyoid 

 muscles are well developed. The longus capitis and colli are represented by a few 

 strands along the anterior surfaces of the vertebral plate. The scaleni medii and 

 posteriores are present as flattened bands of muscle arising in this region and 

 inserted in the first and second ribs near their bases. The scaleni anteriores are 

 symmetrical. They arise from the lateral processes of the superior cervical ver- 

 tebrae and insert on the first rib near its center. The nerve trunks of the cervical 

 and brachial plexus pass under these muscles and are tightly bound down by them. 



Of the more anterior thoracic muscles, the pectorales are not disturbed. Both 

 serati anterior muscles are defective and differ in their defects. On the right side 

 there is more complete development. Here slips of the muscle arising from the 

 distal portions of the first four ribs and from the eighth to the tenth ribs converge 

 and are inserted around the inferior angle of the scapula. A few strands of muscle 

 on the chest wall between the pectoralis minor and the seratus are present, which 

 might be remnants of the latter. They are shaped like half a crescent, with fibers 

 running longitudinally, and extend from the first rib, where they are 3 mm. broad, 

 to the fifth rib,. where they are 15 mm. 



