; 2 PRACTICAL ANATOMY. 



3. The intercostal nerve lies between the pleura and external intercostal 

 muscle. 



4. The nerve throws off muscular branches. 



5. The nerve throws off lateral cutaneous branches. 



6. The nerve is in the substance of the internal intercostal. 



7. The nerve is on the posterior surface of the internal intercostal. 



8. The nerve passes in front of the internal mammary artery. 



9. The nerve throws off anterior cutaneous branches. 



The branches of the intercostal nerve are : (i) Muscular, to the internal and 

 external intercostals, the infracostales, the serratus posticus superior, the triangu- 

 laris sterni, and levatores costarum ; (2) cutaneous branches, lateral and anterior. 

 Now you may find the nerves according to the diagram. You will find the 



Sterno-hyoid 



Sterno-thyroid 



Triangularis 

 aterui 



Sternal origin 

 of diaphragm 



Costal origin 

 of diaphragm 



Triangularis 



Bteriii 



Transversal]! abdominis 



FIG. 142. THE MUSCLES ATTACHED TO THE HACK OK THE STERNUM. 



intercostal arteries with the nerves to some extent. In this dissection care must 

 be taken not to injure the pleura. 



Where to Find the Internal Mammary Artery and Veins. With your forceps 

 go through the soft structures one-half of an inch to the outer margin of the 

 sternum on either side. Try to find this artery, and ligate the same, without 

 injuring the pleura. In reaching this artery, do you cut through the external 

 intercostal muscle? No. Do you cut through the three intercostal fasciae and 

 internal intercostal muscle? Yes. Give the location of the internal mammary 

 artery. It lies between the pleura and internal intercostal fascia. It has two 

 companion veins. 



The Inner Surface of the Sternum and Ribs (Fig. 142). See : 

 I. The internal intercostal muscles, eleven pairs on each side. 



