. Anatomischer Anzeiger. Anatomy, Comparative; Anatomy, Comparative. 56 Between this point and the cranial border of the pons the left a. verte- bralis, or more correctly perhaps the a, basilaris described a gentle curve on the right side of the median plane with its maximum con- vexity 1 cm to the right of the median line; passing thence to the left the vessel regaimed the middle line at the cranial border of the pons and there divided in a perfectly normal manner into two aa. cerebri posteriores. (See Fig. 1.) It is thus clear that the a. basi- laris was not formed by the junction of the two
. Anatomischer Anzeiger. Anatomy, Comparative; Anatomy, Comparative. 56 Between this point and the cranial border of the pons the left a. verte- bralis, or more correctly perhaps the a, basilaris described a gentle curve on the right side of the median plane with its maximum con- vexity 1 cm to the right of the median line; passing thence to the left the vessel regaimed the middle line at the cranial border of the pons and there divided in a perfectly normal manner into two aa. cerebri posteriores. (See Fig. 1.) It is thus clear that the a. basi- laris was not formed by the junction of the two aa. vertebrales but was a direct continuation of the left a. vertebralis, and that the circulus arteriosus (Willisi) was completed posteriorly and was in all respects perfectly normal. N. opticus Chiasma opticum Infundibulum Corpus mamillare Pons, caudal border Medulla oonlbgata Hemisphaerium cerebelli. A. cerebri anterior A. communicans anterior A. carotis interna sinistra A. communicans posterior A. cerebri posterior A. basilaris A. vertebralis dextra A. vertebralis sinistra Fig. 1. Dioptrographic drawing of the abnormal A. basilaris. Natural size. We have already stated that we recognised in a general way that failure of the union of the two aa. vertebrales to form the a, basi- laris was rare, but we were not prepared, until we had made a com- plete survey of the literature of the subject, to find that the condition is apparently one of the very rarest things in anatomical science and that there has been recorded only one case at all similar, that of Batujeff (5). Of the standard anatomical textbooks Morris (6) and Quain (7) make no mention whatsoever of the condition. Piersol (8) states that "very rarely the two vertebrals fail to unite to form a single median basilar, that artery being thus represented by two longitudinal trunks united by transverse anastomoses".. Please note that these images are extracted from scanned page images that may have been digitally e
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