MUSCULAR SYSTEM. 125 



orly, by tendinous fibres, to the two anterior thirds of the crista 

 ilei, and to the anterior spinous process ; superiorly, to the 

 faschia lumborum ; and inwardly, through the medium of its 

 tendon, to the linea alba, throughout its entire extent. 



lie/atious. — Externally, with the panniculus carnosus and pec- 

 toralis magnus ; internally, with the hinder ribs and their carti- 

 lages, and with the obliquus internus and rectus; anteriorly, it 

 digitates with the serratus magnus. 



Direction. — Oblique: from before, backward; and from 

 above, downward. The anterior fibres deviate but little from the 

 horizontal line ; in regard to the others, their obliquity increases 

 from before backwards. 



Structure. — The entire muscle is covered by a dense tendinous 

 expansion, named the apo/ieurosis of the external oblique muscle, 

 which adheres to the fieshy parts through the connection of a 

 delicate cellular tissue, intercepted in places by small slips of ten- 

 don. At the linea semilunaris, however, where the tendon com- 

 mences, the aponeurosis contracts an almost inseparable adhesion 

 to it, accompanying it, thus intimately united, to its termination. 

 Towards the flank, the aponeurosis seems to degenerate into 

 cellular texture. 



The superior and outer parts of the muscle itself are fleshy 

 and digitated ; the inferior and inner parts are tendinous and 

 aponeurotic. The fleshy part grows broader, but becomes thin- 

 ner in substance, posteriorly. 



Remarks. — In the flank, the tendon splits into two portions, 

 which separate, leaving a triangular space or opening between 

 them, whose cavity is obscured by fat and cellular substance. 

 One division of the tendon forms a strong band, which is extended 

 and expended upon the inner side of the thigh ; the other por- 

 tion runs to the ileum, and thence is continued across to the 

 pubes : corresponding in its arrangement and structure to the part 

 called Poupart's ligament in human anatomy, though by no 

 means well defined in the horse. The triangular aperture between 

 these divisions of tendon, which opens into a sort of pouch, closed 

 by the union of these tendons on the outer side, but open towards 

 the pubes, is the abdominal ring: through it, in the male, passes 

 the spermatic chord, from the abdomen into the pelvis; in the 

 female, the rpund ligament passes through it. The aponeurosis 

 is considerably strengthened at this part by some additional ten- 

 dinous fibres, which run transverselj/, from the linea alba towards 

 the ileum. 



Jction. — This pair of muscles, in contributing largely to the 

 foimation of the abdominal parietcs, laterally and inl'eiiorly, give 

 great support to the contained viriccra. In action, they couipress 



