212 



THE MUSCLES OF THE UPPER LIMB. 



clavicle, being inserted into the root of the coracoid process ; or it may have a double inser- 

 tion, the upper into the clavicle, the lower into the coracoid process. A part of this muscle, 

 or occasionally an independent fasciculus, may be inserted into the upper border of the 

 scapula, constituting- the stcrno-scajndai- muscle. 



The fiterno-dnriculfiris extends from the front of the manubrium to the clavicle between 

 the pectoralis major and costo-coracoid membrane. Intermediate forms between this and the 

 pectoralis minimus (p. 211) are also met with. Similar muscles on the two sides have been 

 seen united by a median tendon in front of the manubrium, thus giving rise to a digastric 

 inter clavicular muscle. 



The serratns magnus muscle, placed upon the upper and lateral part of the 

 thorax, between the ribs and the scapula, arises anteriorly from the first eight or 

 nine ribs by as many fleshy slips or digitations, each digitation being attached to the 

 fore part of the outer surface of the corresponding rib, with the exception of the 



Fig. 230. LATERAL VIEW OP THE THORAX, 



SHOWING THE SERRATUS MAGNUS 



MUSCLE. (Allen Thomson.) \ 



, coracoid process of the scapula ; 

 1), glenoid cavity ; c, lower angle ; I, VI, 

 XII, first, sixth, and twelfth ribs ; 1, 

 upper portion of the serratus magnus at- 

 tached to the first and second ribs ; 2, 2, 

 second or middle portion attached to the 

 second and third ribs ; 3, lower or fan- 

 shaped portion attached to the ribs from 

 the fourth to the ninth ; 4, external in- 

 tercostal muscle ; 5, costal origins of the 

 transversalis abclominis. 



first, which is attached to two 

 ribs. Posteriorly, the muscle, 

 considerably narrowed, is inserted 

 into the line in front of the base 

 of the scapula, and at the upper 

 and lower angles of the bone into 

 the flat surfaces which are ex- 

 cluded from the fossa of the sub- 

 scapular muscle. The fibres are 

 arranged in three sets, thus : 

 a, those of the first digitation, springing from the first and second ribs and an inter- 

 vening aponeurotic arch, form a thick bundle which terminates on the flat area in front 

 of the upper angle of the scapula ; #, those of the second and third digitations, from 

 the second and third ribs, but especially the first of these, spread out into a 

 triangular layer, the thinnest part of the muscle, and are attached along the line in 

 front of the base of the scapula, extending from the place of insertion of the pre- 

 ceding part nearly to the lower angle of the bone ; c, the remaining five or six 

 digitations converge in the form of a fan, and terminate posteriorly in a thick mass, 

 which is attached to the flat surface in front of the lower angle of the scapula. 



Relations. By its deep surface, the serratus magnus rests on the upper ribs, the inter- 

 coBtal muscles, and part of the serratus posticus superior. Its outer surface is in contact 

 posteriorly with the subscapular and latissimus dorsi muscles, and forms anteriorly the 

 internal wall of the axilla, being subcutaneous in the lower part of its extent. 



Varieties. Not unf requently the muscle receives a slip also from the tenth rib : on the 

 other hand, the highest digitation often has no attachment to the first rib ; or one or more of 

 the lower digitations may be absent, so that the muscle does, not pass lower than the seventh 

 rib. The muscle has been observed divided into three parts ; sometimes the middle part is 

 defective ; and in various instances the serratus has been observed united partially with the 



