THE CROSSED RESPIRATORY IMPULSES TO THE PHRENIC

Abstract

In animals of several species, under dial anesthesia, spinal semisections at C2 produced ipsilateral respiratory hemiplegias. Section of the active phrenic led to the prompt appearance of crossed diaphragmatic activity in dogs, cats, rabbits and woodchucks. No crossed contractions occurred in monkeys and guinea pigs. Reversible blocks of the phrenic were obtained by means of ether or direct currents. These gave reversible transient crossed contractions similar to those resulting from the sections. The crossed effects in the rabbits, cats and woodchucks are not due to asphyxia. They are not due to the interruption of inhibitory afferent impulses in the phrenics or vagi or sympathetics when the directly activated phrenic is cut or blocked. It is concluded that the crossed phenomenon reveals properties of neurone paths differing in quality from the conduction of nerve impulses: the opening of a new, hitherto unused path, and the tendency for such a path to remain open for relatively long periods of time.