Robert Bennett Bean 317 



SUMMARY. 



I. The branches of the subclavian artery differ in their origin on the 

 two sides of the body, the most frequent arrangement being similar to 

 Type I on the right side, and Type II on the left side. 



(a). The thyroid axis, dividing into the suprascapular, transverse 

 cervical, and inferior thyroid arteries, is not normal, except on the left 

 side. 



(b). The transverse cervical artery and the costo-cervical trunk arise 

 from the second part of the subclavian artery more frequently on the 

 right side than on the left side. 



(c) The superficial cervical artery is of infrequent occurrence, and is 

 found more often on the right side. See Type I. 



(d). The transverse cervical artery terminates by dividing into as- 

 cending and descending rami, the latter being commonly called the pos- 

 terior scapular artery. The former divides underneath the trapezius 

 muscle and supplies the upper and middle part of the back. 



(e). There is a tendency in the branches of the subclavian artery to 

 bunch themselves in their origin on the left side, whereas on the right 

 side there is a tendency in each branch to arise directly from the sub- 

 clavian artery. 



II. There are five important, and not infrequent, anomalies to which 

 the attention is directed : 



(a) The origin of the right subclavian artery from the descending 

 part of the arch of the aorta. This occurs 4-6-8 times in 1000 cases 

 (0.5% to 1% of all persons). 



(b). Variableness in the o]-igin of the transverse cervical artery, 

 especially on the right side. 



(c). The presence of a middle thyroid artery (Thyroidea Ima). 



(d). The suprascapular artery arising from the internal mammary 

 artery. 



(e). The lateral thoracic artery arising from the internal mammary 

 artery. 



III. Eighty per cent of the dissections were made in negro subjects, 

 a large number of whom may have been mulattoes or inixed bloods. 

 That hybrids tend toward variation is a recognized biological law. This 

 may explain the unusually large number of abnormalities encountered. 



IV. Twenty-three infants were dissected and many of these show ir- 

 regularities, particularly in the distribution of the suprascapular artery, 

 wliich is frequently deficient, its place being taken by the dorsal scapular 

 arterv. 



