i8 C. IV. M. Poynter 



view all of the work on development which has a bearing on the 

 problems of these anomalies, but it may be largely covered by con- 

 sulting the following: Baader (1866), Hochstetter (1890), Zucker- 

 kandl (1894-6), DeVriese (1902), Miiller (1902-4-8), Goeppert 

 (1905-8-10), Elze (1913), Evans (1908). 



Ruge (1884) was the first to attempt to arrange these variations 

 in order, and this was very much improved by Schwalbe (1898), 

 based on his comparative work and the developmental studies of 

 Zuckerkandl. Whatever evidence we may have of an early indif- 

 ferent network of capillaries, it is certainly true that somewhat 

 later a definite circulation is laid down, and it seems that it is in 

 connection with this circulation and its elaboration that we must 

 look for the explanation of the anomalies. We must consider the 

 scope of the variations and designate part of them as simply quan- 

 titative, Mehnert (1896). Fischel (1896) and Schwalbe (1898) 

 have shown that even in the earliest embryos there is a large de- 

 gree of individual variation in embryos of the same litter. In 

 explaining any single variation we must look for a series of steps 

 of sufficient breadth to eliminate the individual features and study 

 a sufficiently large series to be sure of their constancy. 



Much of the literature of axillary anomalies relates to high divi- 

 sion of the brachial and other variations of the terminal arteries, 

 consequently the plan already used of considering individual ar- 

 teries will be followed. 



It is not possible to explain all of the various anomalies on an 

 exact embryological basis, due to lack of exact embryological data, 

 but it would seem safe to follow DeVriese (1902) in assuming a 

 secondary plexus for this region. Such an assumption agrees very 

 well with the wide arrangement of branches which we must con- 

 sider normal for this region. Careful measurements show that 

 there is no such thing as arbitrary types and any attempt to force 

 such a classification, while convenient for description, does not 

 represent actual conditions. 



As the first branch from the axillary, Pellegrini found a branch 

 to the serratus anterior present 20 per cent., I found it in 42 per 

 cent. 



