10 



ABDOMEN. 



Above the umbilicus the linea alba is from 

 two to four lines broad in the greater part of its 

 extent; and below the umbilicus it gradually 

 tapers down to the pubis, at the same time in- 

 creasing in thickness.* 



5. Pyramidalis (pubio-sub-umbilical). At 

 the inferior extremity of the recti, and separa- 

 ting their origin, are two small muscles of a 

 pyramidal form; their bases are inferior, and 

 attached to the symphysis and body of the 

 pubis, and uniting ligaments, and their apices 

 superior and inserted into the linea alba by 

 small tendons, from two to three inches above 

 the symphysis pubis. Each muscle is enve- 

 loped in a distinct sheath, and lies a little more 

 prominently than the origin of the rectus of the 

 same side. These muscles are not unfrequently 

 absent. Sometimes, on the contrary, there have 

 been two on one side and one on the other, or 

 even two on each side.-f- 



The muscles which enter into the composi- 

 tion of the posterior wall of the abdomen are 

 chiefly those which occupy the lumbar region 

 of the back, filling up that empty space which 

 in the skeleton is observed on each side of the 

 spinal column between the crista ilii and the 

 last rib. In dissecting from behind forwards 

 in this region, having removed the skin and lax 

 cellular tissue already described, we come upon 

 the strong fibrous expansion, the fascia lumbo- 

 rum. This has extensive osseous attachments, 

 and thus firmly binds down the subjacent mus- 

 cles. When it is removed, the lumbar portions 

 of the sacrolumbalis and longissimus dorsi, and 

 a little of the spinalis dorsi, are brought into 

 view, the two former of which are described by 

 some as a single muscle the sacrospinalis. 

 The external of these muscles is the sacrolum- 

 balis, and its outer margin may be said to con- 

 stitute the limit of the posterior wall of the 

 abdomen in that direction. In this situation 

 the posterior and middle layers of the tendon 

 of the transversalis separate from each other to 

 ensheath these muscles, the posterior layer 

 forming the fascia lumborum. We must refer 

 to the article BACK for a particular description 

 of these muscles. 



When the lumbar mass of muscles (as the 

 three preceding have been called) has been re- 

 moved, the next part brought into view is the 

 anterior layer of their fibrous sheath formed by 

 the middle lamina of the transversalis tendon, 

 which is inserted into the apices of the trans- 

 verse processes. This lamina is thin and semi- 

 transparent, so that the fibres of the muscle 



* " The linea alba performs the same office in 

 the abdomen as the sternum does in the thorax, with 

 this only difference, that it is not formed of bone. 

 The anterior tendons of the broad muscles are at- 

 tached to it, in the same way that the cartilages of 

 the ribs are articulated with the sternum, and the 

 difference of tissue which exists between it and the 

 sternum is attributable to the general difference of 

 structure between the abdominal and pectoral cavi- 

 ties, the latter being formed almost entirely of 

 osseous parts, whilst the walls of the former are 

 fleshy and tendinous." MeckeL 



t Meckel says that this muscle rarely presents 

 anomalies ; in this he must be mistaken, as its ab- 

 sence is certainly not a rare occurrence. 



which lies immediately before it, are seen 

 through it. This muscle is the 



Quadratus lumborum (ilio-costal, ilio-lumbi- 

 costal). The term quadratus is applied to this 

 muscle, more from its quadrilateral form than 

 from any nearer resemblance to a square, in- 

 asmuch as all its sides are unequal. The most 

 fixed attachment of this muscle is its inferior, 

 where it is inserted by tendinous fibres into the 

 iliolumbar ligament and into the inner lip of the 

 crista ilii for about an inch to the outer side of 

 the insertion of that ligament. From these points 

 the fibres proceed vertically upwards, the ex- 

 ternal ones going to be inserted into the inferior 

 margin of the last rib for nearly its entire 

 length, and the internal fibres, those in parti- 

 cular which are attached to the ligament, ter- 

 minating by four aponeurotic tongue-like bun- 

 dles, which are inserted into the anterior surface 

 of the transverse processes of the four superior 

 lumbar vertebrae near their bases. The several 

 bundles which end in these tongue-like pro- 

 cesses vary in length ; those which are external 

 being the longest, as going to higher vertebrae. 

 This muscle is covered on its anterior or abdo- 

 minal surface by the anterior lamina of the 

 tendon of the transversalis muscle, by which it 

 is separated from the diaphragm as well as 

 from the psoas magnus.* The last dorsal 

 nerve and the first two branches of the lumbar 

 plexus, pass between the quadratus and the 

 aponeurotic lamina which covers it. 



Psoas magnus, (4/oa, lumbus) (prelombo, 

 trochanterien, lumbaris.) The greatest por- 

 tion of this muscle belongs to the abdominal 

 region ; it lies along the side of, not only the 

 lumbar but also of a small portion of the dorsal 

 region of the spine, lodged in the angle between 

 the transverse processes and bodies. It passes 

 as high up as the twelfth dorsal vertebra, to the 

 body of which as well as to those of the four suc- 

 ceeding lumbar vertebrae, and to their interven- 

 ing fibro-cartilages, the muscle is attached : it 

 likewise is attached to the bases of the corres- 

 ponding transverse processes, so that the inter- 

 vals between the portions that are attached to 

 the bodies, and those to the transverse processes, 

 correspond to the intervertebral foramina or 

 points of exit of the lumbar nerves, the an- 

 terior branches of which plunge at once into 

 the substance of the psoas muscle to form the 

 lumbar plexus. The several bundles which 

 thus take their origin from the vertebrae form 

 a thick rounded muscle, which passes nearly 

 vertically downwards, inclining a little out- 

 wards, over the brim of the true pelvis, so as 

 often to appear to encroach upon the circum- 

 ference of the upper outlet of that cavity. A 

 little way above Poupart's ligament the mus- 

 cular fibres are inserted around a strong thick 

 tendon. This tendon, which had commenced 

 high up by distinct portions in the interior of 

 the muscle, passes under Poupart's ligament 

 over the horizontal ramus of the pubis. It 

 descends over the capsular ligament of the hip- 



" See fig. 4,/; see also^. 5, where on one side 

 the muscle has been removed from between the 

 laminae of the transversalis tendon. 



