57 



Cunningham (9) says that "the upper end of one of the verte- 

 brals is sometimes very small, or it may be entirely wanting; in the 

 latter case the basilar artery is formed by the direct continuation of 

 the opposite vertebral". 



PoiRiER and Charpy (10) and Testut (11) both quote Batujeff's 

 case, which as it is as yet the only one recorded, is perhaps the most 

 accurate textbook statement of all, whilst lastly the volume dealing 

 with the blood vessels in Bardeleben's great work (12) has apparently 

 not yet appeared. 



Turning next to anatomical literature Cavatorti (13) has described 

 a case somewhat comparable to the condition described in Piersol's 

 textbook. In an examination of 121 cases Cavatorti found in a male 

 aged 78 a somewhat rare variation of the arteries at the base of the 

 brain. The two aa. vertebrales remained separate and ran parallel 

 as far as the caudal border of the pons about 5 mm from the median 

 plane, where they turned laterally in a somewhat twisted manner and 

 terminated on each side as the a. cerebri posterior. The usual 

 anastomosis between the two aa. vertebrales was absent as was also 

 the a. communicans posterior on both sides. The two vessels supplied 

 the cerebellum, medulla oblongata and pons. 



Kendall (14) has described a case in which the aa. vertebrales 

 united as usual to form the a. basilaris; the latter, immediately after 

 its formation, divided into two trunks which again uniting formed 

 a loop; this loop, which was about two lines in length, was situated 

 near the caudal border of the pons Varolii. 



Blackburn (15) in a very careful examination of the blood vessels 

 at the base of the brain in 220 lunatics, found abnormalities in no 

 less than 155 cases. Amongst these abnormalities he found, in two 

 cases, a partial persistence of the embryonic separation of the a. basi- 

 laris into two parts. In five cases he found the bulk of blood passing 

 through the a. vertebralis transmitted into the a. cerebelli inferior 

 posterior. Blackburn has also some interesting remarks anent the 

 calibre of the aa. vertebrales to which reference will subsequently 

 be made. 



Batujeff's (5) case is one of the most remarkable and the best 

 known in the literature of the subject. It occurred in a male aged 

 from 25 to 30 years. The anterior half of the vessels forming the 

 circulus arteriosus (Willisi) was, as in our case, perfectly normal. 

 In the posterior half the a. basilaris was not formed, as it ought to 

 have been by the two aa. vertebrales, but ran, as an unpaired trunk 

 on the left side, through the foramen condyloideum anterius, together 



