Note on the frequency of the bicarotid trunk in the dog

Abstract

In this note, dealing with the frequency of the Truncus bicaroticus in dogs, 5 cases containing the Aa. carótides communes, dextra and sinistra, arising from a single trunk, were found on 139 dissections of the conspicuous collaterals of the aortic arch. The material used comprised adult animals (72 males, 19 females and 4 of unknown sex) and full term foetuses (17 males, 22 females and 5 of unknown sex), summing up to 139 observations, performed mostly in mongrel animals, among which adults presented great variations in age. The 5 cases of T. bicaroticus correspond to 4 males (obs. 5, 9, 14, 65) and 1 female (obs. 128) ; once the verification was stated in a male full term foetus (obs. 65). In 3 other adult exemplars, 1 female (obs. 54) and 2 males (obs. 104 and 135), as the origin of the common carotids and right subclavian arteries from the A. brachiocephalica occurred at the same level, this vessel assumed the aspect of tripod. The T. bicaroticus was present also in two cases (obs. 35, female, adult and obs. 66, female full term foetus), but as an associated disposition related with anomalies of origin and course of the A. subclavia dextra, described in a previous paper. In a group of 6 foetus, one of the males and one of the females exhibited, respectively, T. bicaroticus and right subclavian artery as the last branch of the aortic arch; the rest presented nothing worthy
of note. The interpretation of the findings is based on the study of the development of the branchial arches in pig embryos (Orts Llorca) ; this animal offers both common carotid arteries branching from a single trunk. The interstitial growth and the fusion of the initial tracts of the 4th and 3rd right arches and the 3rd left one, it seems, would determine the constitution of the A. brachioce phalica. Admiting that this fusion may take place accidentally with certain variability and that the interstitial growth between the 3rd arches becomes more intense, all the different dispositions of the A. brachiocephalica collaterals can be traced. The same elements permit other hypothesis to be formulated.