224 THE VOYAGE OF H.M.S. CHALLENGER. 



posterior to the 4th lumbar vertebra and anterior to the anterior ventral spine it has two fascial 

 origins, from the dorsal surface of the erector spina?, and from the tips of the transverse processes of 

 the 5th and 6th lumbar vertebra?. The dorsal border has an oblique direction, sloping gradually 

 from the 1st lumbar vertebra to the anterior ventral spine. The fibres springing opposite the 1st 

 lumbar vertebra pass transversely beneath the digitations of the external oblique from the 13th 

 rib, and are inserted into the posterior border of the 13th rib beneath that muscle; the fibres 

 from the 2nd lumbar spine are similarly inserted into the 14th rib, and those from the 3rd 

 lumbar spine like the last into the 15th rib. The greater portion of the last digitation of the 

 external oblique is blended with the transversalis between the fibres from the 3rd and 4th lumbar 

 spines. Posterior to the 3rd lumbar vertebra the fibres ascend and are inserted into the posterior 

 border of the cartilages of the 13th to the 15th ribs and into the 11th and 12th cartilages by fascia. 

 From the xiphisternum to midway between it and the pubes the fibres end upon the under surface 

 of the rectus ; posterior to this they turn over its ventral surface to end upon it ; and the fibres 

 from the pubes arch over the round ligament and also end upon the rectus. 



The Transversalis abdominis in Phoca vitulina arises from the transversalis fascia between the 

 front of the outer pillar and the anterior ventral spine of the ilium, from the lumbar fascia to 

 the last rib, and from the inner surface of the cartilages of the 10th to the 15th ribs. The fibres are 

 strongest anteriorly and thinnest posteriorly. It is inserted by muscular fibres into the side of the 

 anterior surface of the ensiform cartilage, and blends over its posterior half with its fellow. Behind 

 the ensiform cartilage it forms a tendon which unites with its fellow to the posterior third of the 

 rectus, behind this it ends on the outer side of the rectus. Near the symphysis it terminates upon 

 the transversalis fascia, and near the outer side of the same fascia it crosses over the cord near 

 the internal ring. 



In Arctocephalus it arises from the inner surface of the cartilage of the 11th rib in front of the 

 tip of the 12th rib, from the same part of the 12th to the 15th ribs, from the lumbar fascia coming 

 from the tips of the transverse processes of the lumbar vertebra? ; and between the anterior ventral 

 spine and the pectineal eminence it lies on the transversalis fascia. The fibres are far apart, 

 especially near the pubes, and are inserted into the xiphisternum and the liuea alba; midway 

 between the xiphisternum and the pubes the fibres gradually shorten, and at the posterior fourth of 

 the linea alba they just cross the infundibulum. 



The Rectus abdominis in Phoca vitulina arises from the symphysis and slightly from the brim of 

 the pelvis a little anterior to this. It rims anteriorly over the 11th rib and then along the side of 

 the manubrium. Over the 5th rib it forms a broad thin tendon, which is inserted into the junction 

 of the cartilages with the manubrium from the 1st to the 5th ribs. On the right side the tendon 

 of the rectus was prolonged outwards from the junction of the 1st cartilage with the sternum to the 

 humerus. 



In Arctocephalus it is narrow anteriorly, and arises from the symphysis and the adjacent pubic 

 bar. At the posterior fourth of the muscle it passes between the transversalis and the internal 

 oblique, and midway between the xiphisternum and the pubes between the internal and external 

 oblique. It is inserted by tendinous slips into the outer surfaces of the cartilages of the 5th to 

 the 10th ribs. In Phoca and Arctocephalus the inscriptiones tendinea? are wanting. 



This set of muscles is supplied by the ilio-inguinal, ilio-hypogastric, dorsal, and 1st lumbar 

 nerves. 



