MUSCLES OF THE TRUNK. 205 



the aponeurosis unites with the small oblique, but more particularly with 

 the great oblique, muscle of the abdomen ; it is prolonged, posteriorly, on 

 the muscles of the croup to constitute the gluteal aponeurosis. 



Action. It carries the arm backwards and upwards ; and it may, 

 according to r* great number of authors, serve as an auxiliary in inspiration 

 when its fixed point is the humcrus. According to others, but in whose 

 opinion we do not share, it is an expiratory muscle. 



3. Small Anterior Serrated Muscle. (Fig. 105, 13.) 



Synonyms. Dorso-costalis Girard. Anterior portion of the long serrated muscle 

 Bourgelat. (Superftcialis costarum Percivall. Anterior serrated muscle of Leyh. 

 Serratus posticus superior of Man.) 



Form Situation. This is a flat, thin, and quadrilateral muscle, situated 

 beneath the rhomboideus and the great dorsal muscle. 



Structure. It is composed of an aponeurotic and a fleshy portion. The 

 first is confounded, in front, with the aponeurosis of the splenius, and is 

 insinuated, behind, underneath that of the posterior small serratus, with 

 which it soon becomes united. Its inferior border gives origin to the muscular 

 portion, a little above the interval which separates the common intercostal 

 and the ilio-spinalis. Narrow and elongated antero-posteriorly, the muscular 

 portion is composed of bright-red fibres directed obliquely backwards and 

 downwards, and which form at the inferior border irregular, and sometimes 

 but faintly marked, festoons. 



Attachments. It takes its fixed insertion, by the superior border of its 

 aponeurosis, from the summits of the anterior dorsal spines, with the 

 exception of the first, to the thirteenth inclusive. The movable insertion 

 takes place on the external surface and anterior border of the nine ribs 

 succeeding the fourth, by means of the digitations of the fleshy portion. 

 This muscle is also attached to the external surface of these ribs by a short 

 fibrous band, which is detached from the internal face of the aponeurosis, 

 near its inferior border, and penetrates the space between the ilio-spinalis 

 and the common intercostal muscle. 



Relations. Outwards, with the rhomboideus, great serratus, great dorsal, 

 and the posterior small serratus, which covers its three last festoons ; 

 inwards, with the ilio-spinalis, the common intercostal, and the external 

 intercostals. 



Action. This is an inspiratory muscle, and it also serves as a check to 

 the deep spinal muscles. 



4. Small Posterior Serrated Muscle. (Fig 105, 14.) 



Synonyms. Lumbo-costalis Girard. Posterior portion of the long serrated muscle 

 Bourgelat. (Superficial costarum Percivall. The posterior serrated muscle of Leyh. 

 The serratus posticus inferior of Man.) 



Situation. Situated behind the preceding, which it follows, and present- 

 ing the same form and arrangement, this muscle also offers the following 

 particular features for study : 



1. Structure. Its muscular portion, which is thicker and of a deep-red 

 colour, is cut into nine well-defined digitations. 1 The fibres which compose 

 it run in an almost vertical direction. 



2. A ttacliments. Its aponeurosis, closely united to that of the great dorsal 

 muscle, which covers it, is attached to the spinous processes of the dorsal 



1 It frequently happens that only eight digitations are found. 



