i 4 THE SUPERIOR EXTREMITY 



third of the clavicle, and will be afterwards followed to the 

 skin of the shoulder. They are frequently accompanied by 

 cutaneous branches of the transverse scapular artery. 



Nervi Cutanei Anteriores. The anterior cutaneous nerves 

 are the minute terminal twigs of the anterior rami of the 

 thoracic nerves. They become superficial by piercing the 

 pectoralis major muscle and the deep fascia, close to the 

 margin of the sternum. One will be found in each inter- 

 costal interval except the first ; and they are accompanied by 

 the cutaneous perforating branches of the internal mammary 

 artery, which serve as the best guides to the nerves. The 

 nerves and the arteries give slender twigs to the skin over 

 the sternum, and larger branches which run laterally and 

 may be traced as far as the anterior fold of the axilla. The 

 cutaneous perforating artery which appears through the third 

 intercostal space is usually the largest of the series, especially 

 in the female. 



Nervi Cutanei Laterales. The lateral cutaneous nerves, 

 much larger than the anterior, arise from the anterior rami of 

 the thoracic nerves, and appear, on the side of the thorax, 

 along a line situated a little behind the anterior fold of the 

 axilla. They pierce the wall of the thorax in the interspaces 

 between the ribs, and divide into anterior and posterior 

 branches under cover of the serratus anterior muscle. At a 

 later stage the branches will be found appearing between the 

 digitations of the serratus anterior. The anterior branches 

 appear, as a rule, about an inch in front of the corresponding- 

 posterior branches, and then pass forwards over the lower 

 border of the pectoralis major muscle. From the lower 

 members of this series some minute twigs are given off, which 

 enter the superficial surfaces of the digitations of the external 

 oblique muscle of the abdomen which will be exposed by 

 the dissection of the abdomen. The posterior branches run 

 backwards, to the dorsal aspect of the trunk, over the anterior 

 border of the latissimus dorsi muscle (Fig. 16). 



It is not advisable to attempt to secure the posterior branches of the 

 lateral cutaneous nerves in the meantime. They are best dissected along 

 with the other contents of the axilla. 



The Mamma (Mammary Gland or Breast). In the female 

 the mamma forms a rounded prominence on the front and 

 also, to some extent, on the lateral aspect, of the thorax. It 



