The pyramidal tract of an aquatic carnivore (seal)

Abstract

ONE FIGUREThe mammals, the pyramidal tract of which has not been investigated, are ones not easily obtained, such as the whale, elephant, porpoise, spiny ant-eater, bat, and seal, among others. Each of these has its own special type of motor activity and locomotion, some of it depending upon whether its natural habitat is on land, in the sea or in the air. All are suitable for certain anatomical studies of the pyramidal bundle because it has a consistent and isolated location in the pyramid of the medulla oblongata. By contrast, these hard-to-get animals do not lend themselves easily to physiological laboratory procedures.Although the pyramidal tract has long been considered to be concerned with the innervation of the striated muscles of the body, recent investigations, of an electrophysiological and ablative nature, indicate that it may also serve in the propagation of cortical autonomic impulses from pre-and postcentral areas mediated via small fibers (Brookhart and Morris, '48 ; Landau, '53 ; Spiegel and Hunsicker, '36 ; Spiegel et al., '43). I n the light of this, a spectral analysis of its fibers in any species may be of value in correlating dual types of physiology: transmission of impulses to autonomic as well as to somatic efferent neurons.