On the Aortic Nerves in Cats: The depressor and the pressor nerves

In cats the aortic nerve was examined anatomically and physiologically. Anatomically: In all the cases (42 on the left side and 37 on the right) the aortic nerve was detectable; it has one root (mostly from the upper laryngeal nerve) or two roots (mostly from the upper laryngeal and the vagus), and joins downwards with the vagus trunk, after running isolated in a length of 1-2 cros. in the majority of cases. In one-third of the cases the left aortic nerve runs to its termination without entering into the vagus trunk. The left aortic nerve, which enters into the vagus at the neck, branches again therefrom above the height of the median cervical ganglion. The left aortic nerve is connected with the median cervical ganglion usually by two thin strands. This connection has probably no bearing upon the functioning of the depressor. The left aortic nerve then branches usually into two branchesin the further course and they terminate on the ventral wall of the aortic arc. The right aortic nerve leaves the vagus trunk in the thoracic cavity or at the under neck, sometimes after branching off from the recurrent nerve, sometimes, much above the height of the median cervical ganglion. It branches in the further course into two or three nerve strands, and they terminate at the dorsal wall of the aortic arc, but some fibres run further to the lateral wall of the innominate artery, the right heart ventricle and the pulmonary artery. Physiologically: At the neck the aortic nerve is long enough to be stimulated in the majority of cases; it is needless to say that it is to be isolated in a sufficient length for stimulation in the thoracic cavity. The left aortic nerve causes always a fall of the arterial pressure reflexly; the pulse rate diminishes usually, but its scale is decidedly smaller compared with rabbits and dogs. The right aortic nerve always causes an elevation of the arterial pressure, contrary to the left; the heart beat rate is not affected at all, in contrast to a common afferent nerve, which gives rise to an accelerated heartbeat besides the blood pressure elevation. From this reasoning and the anatomical homology with the left side nerve, we are apt to take this right aortic nerve as having some particular bearing upon the blood pressure regulation, as the left aortic nerve, the depressor, but in reverse direction with the latter. In conclusion, it may be added that this right aortic nerve, which may be named as the pressor nerve, does not, as may be expec