196 MUSCLES OF THE UPPER LIMB 



platysma myoides and by the mamma. The posteiior sui'face rests chiefly on the 

 pectoralis minor, and with that muscle foims the anterior wall of the axilla. 



Varieties.— The more important varieties of this muscle consist in the gr-eater 

 or less extent of its attachments to the ribs or sternum, and the greater or less 

 union or separation of its clavicular, sternal, and costal paits. The clavicular 

 part has occasionally been observed to be absent, or to be incoiporated completely 

 with the deltoid. The tendinous and fleshy fibres of origin of opposite sides 

 sometimes meet and even decussate in front of the sternum. In some instances 

 atlditional muscular slips take origin from the aponeurosis of the external oblique 

 mui^cle. and in others the lower part of the muscle presents considerable deficiency. 

 Sometimes also slips connect the great pectoral with the biceps muscle. The 

 slips of connection with the latissimus dorsi have already been noticed. 



As closely related to the great pectoral muscle there may be noticed here the 

 muscular band which has been obsei-ved by Wood, Stnithers, Macalister, and 

 others, passing from a fascial origin over some of the lower tnie and upper false 

 ribs to a very variable tendinous or aponeurotic insertion at some place along the 

 inner border of the arm, or even as far down as the inner condyle of the humei-us, 

 and which has been named chond'ro-c2)itroc]ilcari>!. 



The pectoralis minor muscle arises from the upper margins and 

 external surfaces of three ribs near their cartilage.s — usually the third, 

 fourth, and fifth — and from the neighbouring parts of the intercostal 

 aponeurosis. Its fibres converge to a narrow tendon, which is inserted 

 into the anterior half of the inner border and upper surface of the 

 coracoid process, in contact with the conjoined origin of the coraco- 

 brachialis and biceps muscles. 



IMations. — This muscle is covered by the pectoralis major, and forms a part of 

 the anterior wall of the axilla. It crosses the axillary artery and brachial plexus 

 of nerv^es. When tlie ann is much raised a portion of the muscle may be seen 

 below the outer margin of the pectoralis major. 



Varieties. — The pectoralis minor is sometimes found split up or subdivided 

 into as many pieces as it has of costal attachments. The place and number of 

 the costal slips are subject to slight variation. The tendon of insertion is not 

 Tinfrequently detached from the coracoid process, and carried on by the coraco- 

 acromial ligament to the acromion process or some other neighbouring part. 



The subclavius muscle arises by a short thick tendon from the first 

 costal arch at the junction of the rib and cartilage, close to the costo- 

 clavicular ligament. From this tendon its fibres pass outwards and 

 upwards, forming a rounded belly, which is inserted into the groove 

 along the inferior surface of the clavicle, extending as far as the recess 

 between the conoid and trapezoid parts of the coraco-clavicular ligament. 



Ih'lafions. — The subclavius is covered in front by the costo-coracoid fascia, and 

 is placed immediately over the axillary vessels and nerves. 



Varieties. — The subclavius is sometimes found to be without any attachment 

 to the clavicle, being inserted into the root of the coracoid process ; or it may 

 have a double iasertion, the upper into the clavicle, the lower iato the coracoid 

 process. 



The serratus niagixus muscle, placed upon the upper and lateral 

 part of the tliorax, between the ribs and the scapula, is attached 

 anteriorly by nine fleshy angular slips to the first eight or sometimes 

 nine ribs, two of these being connected with the second rib ; it also 

 derives some fibres from the aponeurosis covering the upper intercostal 

 spaces. Posteriorly, the muscle, considerably narrowed, is attached to 

 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 excluded from the 

 fossa of the subscapular muscle. The fibres are arranged in three sets,. 



