316 A Composite Study of tlie Subcliiviau Arti-ry in Man 



tions is the suprascapular artery arising from the internal mammary 

 artery (see Fig. G). This occurs fi times in 104 cases (practically 

 12%). Quain " found the same anomaly 4 times in 264 dissections 

 of the subclavian artery (about 1%). Arthur Thomson" found it 9 

 times in 544 cases (less than 2%). Another anomaly is found in con- 

 nection with the internal mammary artery. The latter divides into two 

 branches a few cm. from its origin, one of which takes the normal course 

 of the internal mammary artery, while the other follows the anterior 

 axillary line between the ribs and pleura, terminating at the diaphragm 

 in two cases, at the fourth rib in three other cases. This branch is as 

 large as the ordinary internal mammary artery, and. sends branches into 

 the intercostal spaces just as that artery does. This " lateral thoracic 

 artery" is present 5 times in 28 cases (18%) that are carefully worked 

 out. Anatomists mention this anomaly, but consider its occurrence 

 much rarer than our findings indicate. Another important anomaly is 

 observed twice. The anomaly is in the trunks arising from the arch of 

 the aorta. Tb.e first trunk divides immediately at the aorta into the two 

 common carotid arteries. The second trunk is the left subclavian artery. 

 The third trunk is the right subclavian artery. This arises from the 

 distal part of the aortic arch on a level with the fourth thoracic vertebra, 

 and passes posteriorly between the oesophagus and the vertebral column 

 to its usual place on the right side. The right recurrent laryngeal nerve 

 passes directly to its distribution, without looping around tlie subclavian 

 artery. The pneumogastric and phrenic nerves occupy their usual places 

 and relations. This anomaly has been reviewed by Gotthold Holzapfel,*" 

 who collected 200 cases from the literature, including 4 of his own (1 in 

 an animal). He concludes that this anomaly occurs 6 times in every 

 1000 cases. Quain and other anatomists fixed the ratio at 4:1000. 

 Tiedemann gives the ratio 8:1000, nearly 1%. The middle thyroid 

 artery, " Thyroidea Ima," another anomaly, is found three times. It 

 arises from the innominate artery, and, passing to the median line, 

 supplies the lower lobes of the thyroid gland and the isthmus. Wenzel 

 Gruber " records 125 anomalies of this kind, and concludes that the artery 

 rises most frequently from the innominate artery, Imt also not infre- 

 quently comes from the aorta and the common carotid artery. He found 

 it 16 times in 100 consecutive dissections. 



" Quain, Commentaries on the Arteries, London, 1844. 



" Thomson, Second Report of the Collective Investigation of the Ana- 

 tomical Society of Great Britain and Ireland. Journal of Anatomy and 

 Physiology, London, Vol. XXVI, p. 78. 



"Holzapfel, Anatomische Hefte, XII, I part, p. 373 (1S97). 



" Gruber, Virchow's Archiv, Vol. 54, p. 445. 



