On the behavior of the lumbo-spinal dog.

Abstract

Dogs whose spinal cords are completely sectioned between the 1st and the 3d lumbar roots immediately undergo profound bodily changes below the level of the lesion. Not only is muscular tonus reduced but electrical resistance drops to nearly 1/10th its preoperative value, where it remains indefinitely. The lumbo-spinal prepn. is nevertheless capable of complex and extensive movements, many of which are equivalent to those performed by intact animals. In addition to localized reflexes, these include the assumption of the complete posture for defecation and for micturition (in the [female] ), as well as momentary standing without any support or aid. The most complex behavior apparently involves coordination between parts of the body above and below the level of the lesion. If this coordination is not an artifact, it may take place in any of the following ways: 1) By means of afferent fibers through autonomic path-ways which circumvent the transection. 2) By the overlapping of the ends of motor fibers from centers below the transection with the ends of proprioceptive fibers from centers above the transection. 3) By mechanical pulling or stretching of the skin and muscles above the level of the transection, as a result of muscular activity below the transection.