4 C. W. M. Poynter 



Lang (1856) became convinced from a study of the enervation 

 of blood vessels that they must be as important morphologically as 

 other structures of the body, while Marshall (1850), Hochstetter, 

 and many others showed that the persistence of certain embryo- 

 logical stages might, through arrest of development, account for 

 many of the familiar variations. The next significant work was 

 that of Miller & McWhorter (1914), which demonstrated the for- 

 mation of the embryological vessels in situ. It has been shown by 

 Loeb, Stockard, Reagan, Webber, and others that the circulation 

 of the blood is not necessary to the development of the vessels, and 

 also that vascular irregularities are correlated with other structural 

 irregularities in developmental disturbances. 



In the regions where the stages of the development of the blood 

 vessels have been worked out the data furnishes a satisfactory basis 

 for the explanation of the adult variations usually encountered. It 

 would seem, in the light of the more recent embryological investi- 

 gations, that we are warranted in considering vascular anomalies 

 as teratological problems. They are interesting as indicating de- 

 velopmental disturbances, kinship between man and the other 

 animals, and wide adaptability within the organism. They are of 

 slight practical value to the modern surgeon with his perfected 

 technique and are by no means as limitless in number of patterns 

 as the postulate of Baader would indicate. 



ARTERIES OF THE HEAD AND NECK 



ARTERI^ 



A. Car Otis Cominunis 



In a former monograph on the aortic arches I have covered the 

 various origins of this vessel ('16, p. 41). There is occasionally 

 great variation of the caliber on the two sides and also at different 

 levels of the individual trunk. Stahel (1886) found a constant 

 contracture of the proximal portion and Biswanger (1879) found 

 that adults acquired a dilation near the bifurcation whicli was 

 carried on into the beginning of the internal carotid. The length 

 of the vessel shows a wide variation, but measurements have not 

 been made on a sufficiently large number of cases to be of any 



