ABDOMEN. 



9 



and the external, the largest of the three, 

 into the inferior edge of the cartilage of the 

 fifth rib. This muscle is remarkable for its 

 tendinous intersections, which cut the fibres at 

 right angles, and are called linea transverse. ;* 

 they vary in number from three to five, and are 

 always more numerous above than below the 

 umbilicus. In general there is one on a level 

 with the umbilicus ; the superior one being 

 about an inch below the superior attachment of 

 the muscle, and a third midway between these 

 two : when a fourth and a fifth exist, they are 

 below the umbilicus. They adhere to the an- 

 terior wall of the sheath closely, and but very 

 slightly or not at all to the posterior. Some- 

 times the intersection does not go completely 

 through the thickness of the muscle so as to 

 appear on its posterior surface, and thus the 

 posterior fibres are longer than the anterior ; 

 but as Bichat remarks, it never happens that 

 any of the muscular fibres pass from one extre- 

 mity of the muscle to the other without 

 uniting at least one of these intersections. 

 Sometimes, too, the intersection does not go 

 through the breadth of the muscle, and this is 

 generally the case with that below the umbili- 

 cus. The effect of these intersections is to 

 convert the muscle into so many distinct bellies, 

 each of which has its proper action, and is, as 

 Beclard asserts, provided with a separate 

 nerve.f 



The rectus muscle is enveloped in a fibrous 

 sheath, the mode of formation of which the 

 reader must have collected from the description 

 of the oblique muscles. The anterior wall of 

 this sheath is formed by the aponeurosis of the 

 external oblique alone over the chest, and by the 

 same aponeurosis and the anterior layer of that of 

 the internal oblique, from the xiphoid cartilage 

 to the inferior fourth of the muscle ; (both which 

 aponeuroses over the internal half of the muscle 

 are so adherent to each other as to form but 

 one lamina;) and in its inferior fourth by the 

 conjoined aponeuroses of the two obliqui and 

 transversalis. 



The posterior wall of the sheath is deficient 

 superiorly where the muscle covers the carti- 

 lages of the ribs with which it is in contact, 

 and inferiorly for a space corresponding to the 

 inferior fourth of the muscle. So much of it as 

 exists is formed by the tendon of the transver- 

 salis and the posterior lamina of that of the 

 internal oblique, so that the rectus appears to 

 have passed at its inferior extremity through a 

 transverse slit in these conjoined tendons, so as 

 to get between them and the peritoneum. 



The rectus muscle covers, at its superior ex- 

 tremity, the cartilages of the two last true ribs 

 and a part of those of the two first false, and 

 also the xiphoid appendix. The internal mam- 

 mary and epigastric arteries are found behind it 

 in the sheath. 



Between the recti muscles is the fibrous cord 

 called linea alba, produced by the interlace- 



* Also called enervations. Winslow. They are, 

 says Meckel, incontestably incomplete repetitions of 

 the ribs in the walls of the abdomen. 



t Hence Meckel classes it among the polygastric 

 muscles. 



ment of the aponeuroses of the opposite sides, 

 noted in surgery as being in its inferior half the 

 seat of the operations of paracentesis abdominis, 

 paracentesis vesicae supra pubem, the supra- 

 pubic lithotomy, and the Csesarean operation. 

 This cord extends from the xiphoid cartilage to 

 the symphysis pubis, with the anterior liga- 

 ment of which articulation it is identified. It 

 does not present the same breadth in its whole 

 course, being broader in the umbilical region 

 than elsewhere. In this region we find in the 

 linea alba the perforation which gave passage to 

 the umbilical vessels in the foetus and the 

 urachus, and through which the fibrous remains 

 of those vessels pass to be inserted into the 

 skin, whereby is formed the cutaneous depres- 

 sion which marks the situation of this opening. 

 In the adult the umbilicus may be considered 

 as a point of considerable strength ; in the esti- 

 mation of some it is the strongest point in the 

 abdominal parietes : in dissecting away the skin 

 at this point, we find subjacent to it a very con- 

 densed cellular tissue, to which and to the 

 skin the fibrous cords into which the umbilical 

 vessels have degenerated adhere closely ; these 

 cords, too, adhere not only to the skin, but 

 likewise to the margin of the fibrous ring 

 through which they pass. " The umbilical 

 opening, therefore," says Scarpa, " in the 

 infant two months after birth, and still 

 more in the adult, is not only like the other 

 natural openings of the abdomen, strength- 

 ened internally by the application of the peri- 

 toneum and of the cellular substance, and on 

 the outside by the common integuments, but it 

 is likewise plugged up in the centre by the 

 three umbilical ligaments and by the urachus ; 

 these ligaments form a triangle, the apex of 

 which is fixed in the cicatrix of the integuments 

 of the umbilicus, the base in the liver, in the 

 two ilio-lumbar regions, and in the fundus of 

 the urinary bladder ; by this triangle is formed 

 a strong and elastic bridle, capable of itself 

 alone of opposing a powerful resistance to the 

 viscera attempting to open a passage through 

 the aponeurotic ring of the umbilicus, which 

 apparatus does not exist at the inguinal ring or 

 femoral arch."* 



In the foetus the ring of the umbilicus is 

 proportionally larger than at any period after 

 birth when the cicatrix is fully formed : it is, 

 however, at the full term, or even at the seventh 

 or eighth month, and in the healthy state of the 

 parts, equally filled up by the umbilical vessels 

 and urachus, and we would say is equally 

 capable of resisting intestinal protusion as at 

 any subsequent period. Hence it may be in- 

 ferred that congenital umbilical ruptures are 

 always of very early date, being attributable to 

 the persistence of the opening at the umbilicus, 

 and the continuance in it of the intestinal pro- 

 longation which exists there naturally at a very 

 early period. It may likewise be inferred that 

 the rupture in the adult can much more easily 

 occur in the vicinity of, than through the umbi- 

 lical ring; and experience confirms this deduc- 

 tion from the anatomy of the parts. 



* Scarpa on Hernia, p. 373. 



