262 THE MUSCLES. 



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 a great number of authors, serve as an auxiliary in inspiration when its fixed 

 point is the humerus. According to others, but in whose opinion we do not 

 share, it is an expiratory muscle. 



Second Layer. 



3. Small Anterior Serrated Muscle (Serratus Anticus) (Fig. 162, 13). 



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

 Bourgelat. (Superficialis costarum — Percivall, Anterior serrated muscle of Leylj. Serratus 

 posticus superior of Man.) 



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

 the rhomboideus and the latissimus dorsi. 



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 transversalis costarum and the longissimus 

 dorsi. Narrow and elongated antero-posteriorly, the muscular portion is com- 

 posed of bright-red fibres directed obliquely backwards and downwards, 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 longissimus dorsi and the transversalis costarum. 



Relations. — Outwards, with the rhomboideus, serratus magnus, latissimus dorsi, 

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

 with the longissimus dorsi, the transversalis costarum, 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 (Serratus Posticus) (Fig. 162, 14). 



Synonyms.— Jjumho-coHtalis— Girard. Posterior portion of the long serrated muscle — 

 Bou/gelat. (Superficialis costarum — Percivall. The posterior serrated muscle of Leyh. The 

 serratus posticus inferior of Man.) 



Situation. — Situated behind the preceding, which it follows, and presenting 

 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.^ The fibres which compose it run in an 

 almost vertical direction. 



' It frequently happens that only eight diiritations are found in each muscle. 



