244 THE MUSCLES. 



sections. These strongly adhere to the aponeurosis of the small oblique 

 muscle, are nearer to each other, and more distinct, in front than behind, 

 and are produced by small tendons which are. placed at certain distances on 

 the track of the muscular fasciculi, making it somewhat of a polygastric 

 muscle. 



Attachments. — In front : 1, To the prolonging cartilages of the last 

 four sternal, and the first asternal ribs; 2, To the inferior face of the 

 sternum. Outwardly, by the anterior moiety of its external border, to the 

 internal face of the great oblique. 



Behind, to the anterior border of the pubis through the medium of the 

 common tendon, which is a direct continuation of the great straight 

 muscle. , 



Belations. — By its inferior face, and in front, with the sterno-trochineus 

 and great oblique ; for the remainder of its extent, with the aponeurosis of 

 the small oblique. By its superior face, with the transverse muscle and 

 the cartilages of several ribs. By its internal border, with the white line, 

 which separates it from the opposite muscle. 



Action. — It draws the thorax backwards, and compresses the abdominal 

 viscera. It is also the principal flexor of the spine. (Leyh, remarking that 

 it shares in the functions of the preceding muscles, adds that it draws the 

 pelvis forwards during copulation.) 



6. Transverse Muscle of the Abdomen. (Figs. 106, 18 ; 116, 3'.) 



Synonyms. — Lumbo-abdominalis — Girard. ( Transversalis abdominis — PercivaU. 

 The costo-ahdominalis internus of Leyli.) 



Situation — Composition. — This muscle is situated immediately without 

 the peritoneum, and forms the deep layer of the abdominal parietes. It is 

 muscular outwardly, and aponeurotic for the remainder of its extent. 



Form, Structure, and Attachments of the muscular portion. — It presents a 

 band elongated from before to behind, extending from the sternum to the 

 transverse processes of the last -lumbar vertebrae, following in its course the 

 direction of the cartilages of the ribs, and formed of parallel fibres passing 

 from one border to the other. 



Its superior border, concave, is attached : 1, To the internal surface of 

 the asternal ribs by digitations placed opposite those of the diaphragm, hut 

 the majority of which do not mix with them ; 2, To the extremity of the 

 transverse processes of the lumbar region by a thin fibrous lamina. Its 

 inferior border is convex and continuous with the aponeurosis. 



Form, Structure, and Attachments of the aponeurosis. — This is triangular- 

 shaped, with the base behind, and with its fibres running in a transverse 

 direction to the median line. Closely laid one against another in front, 

 these fibres separate behind, and form only a very thin and incomplete 

 lamina. 



By its external border, the aponeurosis is joined to the inferior margin 

 of the muscular portion. Its internal border is fixed to the xiphoid cartilage 

 and the white line. Its posterior border, badly defined, appears to join the 

 crural arch only on its outer aspect. 



Belations. — Outwards, with the inferior extremity of the asternal ribs 

 and their cartilages, with the rectus abdominalis, the small oblique, and the 

 depressor muscle of the last rib ; inwardly, with the peritoneum, from which 

 it is separated by the subperitoneal aponeurosis : an extremely fibrous layer 

 which, in Man and some animals, becomes much thickened towards the crural 



