226 LABORATORY MANUAL OF HUMAN ANATOMY 



(d) Smallest scalene (M. scalenus minimus] (inconstant). 



Study the relation of these to surrounding structures and note espe- 

 cially the very important structures related to the most anterior of the 

 three muscles. 



Arteries. 



(a) Subclavian artery (A. subclavia). (Vide Fig. 16.) 

 Branches : 



Medialward from the M. scalenus anterior. 



(aa) Vertebral (A. vertebralis) . 



(ab) Internal mammary (A. mammaria internet). 



(ac) Thyreocervical trunk (truncus thyreocervicalis) . 



(aca) Inferior thyreoid (A. thyreoidea inferior}. 



(acb) Ascending cervical (A. cervicalis ascendens). 

 (ace) Superficial cervical (A. cervicalis superficialis) . 

 (acd) Transverse scapular (A. transversa scapulae). 



Behind the M. scalenus anterior. 



(ad) Costocervical trunk (truncus costocervicalis) (0. T. supe- 



rior intercostal). 



(ada) Highest intercostal artery (A. intercostalis su- 



prema) (0. T. superior intercostal proper). 



(adb) Deep cervical artery (A. cervicalis profunda). 

 Between the Mm. scaleni. 



(ae) Transverse artery of neck (A. transversa colli). 

 Veins. 



(a) Right and left innominate veins (Vv. anonymae dextra et sinistra). 



(aa) Inferior thyreoid veins (Vv. thyreoideae inferiores). 



(ab) Inferior laryngeal vein (V. laryngea inferior}. 



(ac) Lowest thyreoid vein (V. thyreoidea ima). 



(ad) Unpaired thyreoid plexus (plexus thyreoideus impar). 



(ae) Vertebral vein (V. vertebralis) . 



(aea) Deep cervical vein (V. cervicalis profunda). 



(b) Lower part of internal jugular vein (V. jugularis interna). 



(ba) An inferior thyreoid vein (V. thyreoidea inferior). 

 Note the bulbus venae jugularis inferior. 



(c) Subclavian vein (V. subclavia). 



(ca) Thoraco-acromial vein (V. thoraco-acromialis) . 



(cb) Transverse vein of neck (V. transversa colli). 



Lymphatics. 



(a) Thoracic duct (ductus thoracicus). (Vide Fig. 93.) 



(b) Right lymphatic duct (ductus lymphaticus dexter). 



These may easily be mistaken for veins when first met with by the 

 student. 



Nerves. (Vide Fig. 92.) 



(a) Phrenic nerve (N. phrenicus). Why should this nerve, arising in 



the neck, supply a muscle situated at the lower opening of the 

 thorax? 



(b) Vagus nerve (N. vagus). Note its relation to the M. scalenus ante- 



rior, the trachea, and the A. carotis communis. 



(c) Lower part of cervical part of sympathetic trunk (truncus sym- 



pathicus). 



