402 LABORATORY MANUAL OF HUMAN ANATOMY 



(bbb) Lateral cutaneous rami (rami cutanei later ales [pec- 



torales et ab dominates]). 



(bbba) Posterior ramus (ramus posterior). 



(bbbb) Anterior ramus (ramus anterior). 



(bbbc) Lateral mammary rami (rami mammarii 



later ales). 



(bbc) Anterior cutaneous rami (rami cutanei anteriores 



[pectorales et ab dominates]) . 



(be) Medial mammary rami (rami mammarii mediates). 

 (c) Intercostal veins (Vv. intercostales) . 



Note that they run above the arteries in the sulci costarum. 

 Their posterior relations will be studied later. 



Internal Mammary Artery (A. mammaria interna). (Vide Fig. 9.) 



Remove the intercostal muscles, but work most cautiously, 

 and be sure to avoid injury to the subjacent pleura, which must 

 be preserved intact and left undisturbed in contact with the 

 internal surface of the ribs. Clean the A. mammaria interna and 

 the outer surface of the M. transversus thoracis. Observe how 

 far down the pleura passes in the recess between the diaphragm 

 and the costal arches. Below the pleura do not mistake the dia- 

 phragm for unremoved intercostal muscles. 



Examine the following branches of the A. mammaria interna : 



(a) Sternal rami (rami sternales). 



( b ) Perforating rami ( rami perforantes ) . 



(ba) Mammary rami (rami mammarii). 



(bb) Muscular rami (rami musculares). 

 (be) Cutaneous rami (rami cutanei). 



(c) Intercostal rami (rami intercostales) (0. T. anterior intercostals). 



(d) Musculophrenic artery (A. musculophrenica) . 



(e) Superior epigastric artery (A. epigastrica superior}. 



Note that (d) and (e) are terminal branches, the bifurcation 

 usually occurring in the sixth intercostal space ; the sixth costal 

 cartilage may be excised in order to display this better. The 

 anterior mediastinal, thymic, bronchial, and pericardiacophrenic 

 branches of the internal mammary artery cannot be studied until 

 later. 



Transverse Muscle of Thorax (M. transversus thoracis) (O. T. Tri- 

 angular is Sterni). 



Study this muscle as far as is possible at the present stage of 

 the dissection. It will be better exposed later.' 



