CHAPTER I. 



DISSECTION OF THE ANTERIOR LIMB. 



THE PECTORAL REGION AND THE AXILLA. 



As the first step in the examination of the fore limb, the student 

 should dissect the structures which pass between the trunk and the 

 ventral aspect of the limb. 



Position. — The subject should be placed on the middle line of its 

 back, and its limbs should be forcibly drawn upwards and outwards by 

 ropes running over pulleys fixed to the ceiling. If only one side is 

 being dissected the subject may be inclined as in Plate 1. This will 

 put the muscles and other structures on the stretch, and thus facilitate 

 their dissection. 



Surface-marking. — In the fore part of the pectoral region the student 

 will notice the well-marked prominence formed by the anterior super- 

 ficial pectorial muscle. Between this muscle and the lower edge of the 

 mastoido-humeralis there is a groove in which will afterwards be 

 dissected the cephalic vein and a branch of the inferior cervical artery. 

 Extending inwards from the point of the elbow is a prominent fold of 

 skin over the hinder edge of the* posterior superficial pectoral muscle. 



Directions. — An incision through the skin, but not deeper, is to be 

 made along the middle line of the sternum, from the ensiform cartilage 

 as far forwards as the cariniform cartilage. From the middle of this 

 incision another is to be carried transversely outwards, and terminated 

 a little beyond the elbow-joint. Where this second incision stops, 

 another is to be made across the inner face of the fore-arm. Beginning 

 at the point where these incisions meet, the student should raise and 

 turn outwards the two flaps of skin, so as to denude the superficial 

 pectoral muscle. In doing this, it may be noticed that here, as in other 

 unexposed situations, the skin is comparatively thin. Beneath the skin 

 is the subcutaneous fascia, and search is to be made in it for the 

 cutaneous nerves of this region. 



Cutaneous Nerves. A nerve of considerable size, derived from the 

 6th cervical nerve (Plate 1), crosses the groove between the mastoido- 

 humeralis and the anterior superficial pectoral, and distributes branches 

 to the skin over the latter muscle and part of the posterior superficial 

 pectoral. Other small cutaneous twigs, which are branches of the 



B 



