Three Cases of Defect of the Left Common Carotid Artery in the Rabbit

In three individuals (#1, #2, and #3) among 906 adult rabbits, in which vascular casts and dissection specimens of the whole vascular system prepared by acryl plastic injection were examined, the left common carotid artery was found to be defective.The aortic arch in each of these three cases was located at a normal height. The branches of the arch in usual cases in the rabbit were the brachiocephalic trunk and the left subclavian artery. This trunk trifurcated into the left and right common carotid arteries and the right subclavian artery, as seen in Type B of man (Adachi 1928). However, the left common carotid was not observed in each of the examples reported here. In the third example (#3), which was a dissection specimen, a remnant consisting of a connective tissue cord, instead of the left common carotid, was found. The right common carotid and right external carotid arteries were thicker than those observed in usual cases without any variations in their course and ramifications. The lingual artery in each of the three examples was rather thick and anastomosed strongly via a thick, hyoid branch with its opposite fellow. The left common carotid appeared as a fine vessel passing caudally from the bifurcation of the common carotid artery and became a fine cord of connective tissue which joined the brachiocephalic trunk. The bilateral lingual arteries were thick and anastomosed with each other. The hyoid branch of the lingual artery of the rabbit was always thick Through this anastomosis, the blood supply to the left half of the head was performed by ramifications of the right external carotid. It can thus be said that, prior to closure of the left common carotid, the above-mentioned anastomosis would have become much stronger.