DISSECTION OF THE NECK. 63 



tertius ; it arises from the transverse process of the 

 7th cervical vertebra. 



4. The Intercostal Muscles. Remove the above- 

 named muscles and fat, etc., from the thorax ; the in- 

 tercostal muscles lying between the ribs will be ex- 

 posed. 



a. The External Intercostals form the external 

 layer passing from the posterior margin of one bony 

 rib to the anterior margin of the succeeding one ; the 

 fibres have an inclination inward and to the posterior. 

 This layer ceases at the cartilaginous ribs. The layer 

 of muscle between these portions of the ribs forms 

 the mtercartilagmoiis muscles, and their fibres have an 

 inclination in the opposite direction. 



b. The Internal Intercostals. Dissect off the 

 external intercostals between two or three of the ribs, 

 and the internal intercostals will be exposed ; these 

 also pass from one bony rib to the other, but have an 

 inclination outw^ard and to the posterior. 



DISSECTION OF THE NECK. 



Make ail incision along the mid-line of the neck 

 tJiJ'oiigh the skin, and the necessary transverse incis- 

 ions at the shoulder. Lay back the flaps of skin o?i 

 both sides. 



I. The Platysma Myoides is a skin-muscle found 

 in the neck which may have been reflected with the 

 skin. The chief bundle of fibres in it arises from the 

 dorsal wall of the anterior portion of the thorax, and 

 comes obliquely around to the ventral surface of the 

 neck, and continues forward to the head. Scattered 

 muscular fibres pass transversely from this during its 

 course toward the ventral mid-line of the neck. The 

 muscle is attached only to the skin. 



