14 C. W. M. Poynter 



shif tings actually revealed by measurements. Pellegrini uses 

 graphs which suggest quantitative study, although none was at- 

 tempted. The branches of the subclavian show such a wide vari- 

 ation in their arrangement and the shifts of origin are so gradual 

 and independent of each other it seems best to follow the plan of 

 the earlier writers and treat each branch separately. 



It is difficult to establish the number and identity of branches. 

 Pellegrini found that there could be as many as 12 separate 

 branches and placed the normal number as 10. Bean found the 

 number of branches greater in adults than in infants, due, appar- 

 ently, to the grouping as axes in the latter ; he also found a differ- 

 ence in arrangement between the two sides. I found that the 

 weighted average number of branches in my series was 4 : 93, rep- 

 resenting a wide variety of combinations and dissimilarity between 

 the right and left sides. 



A. Vertebralis 

 See Study, 1916, p. 41. 



A. M ammaria Interna 



This artery is constant, but shows wide variations of origin and 

 relations to other vessels. It may arise from the aorta or in- 

 nominate, Neubauer (1722), Boehmer (1741), Walther (1785), 

 Meckel (1816), Tiedemann (1822). Gruber (1872), In this 

 series the condition was observed twice in the same cadaver ; there 

 was a second artery on the right with normal origin. The artery 

 may arise lateral to the scalenus anticus and pass either ventral or 

 dorsal to it, Miinz (1821), Lauth (1833), Labatt (1837), Quain 

 (1844), Nuhn (1849), Schwegel (1859), Power (i860), Gruber 

 (1872). 



Its course in the chest in relation to the border of the sternum 

 shows a variation from 5 mm. to 35 mm. Its intercostal branches 

 in their number, extent and anastomoses show a wide latitude. 



A lateral internal mammary was described by Otto (1824) under 

 the name of ramus costalis lateralis. It may spring from the sub- 

 clavian as a separate branch or from the internal mammary, or, as 

 in a case I encountered, it may spring from the third portion of 



