STUDIES IN DECEREBRATION

Abstract

In 4 cats, the first 23, 20, 18 and 21 posterior spinal roots were divided intradurally on both sides; in each animal both forelegs were deaf-ferented completely. The animals were decerebrated by the anemic method 3 wks. afterward; the spinal cord was then transected at a level one segment above the last pair of sectioned roots. After decerebration, the animals developed marked extensor rigidity in all extremities (persisting in the forelegs after the spinal cord was sectioned) as long as the animal''s head remained in a position with the occiput down. A pressure of 800 gm. was needed to produce flexion of the extended forelegs. Turning the head to one side was followed by diminution of extensor tone in the opposite foreleg. The experiment demonstrates that in so far as the forelegs are concerned, strong extensor rigidity in a decerebrate animal is produced directly by labyrinthine reflexes without the existence of any tonus produced by a stretch reflex. Decerebrate rigidity is due, therefore, to a summation of reflex activities, of which the stretch reflex represents but a small part.