The discovery of the inhibitory Golgi tendon organ reflex provided the first real evidence of neural inhibition Long before the synaptic mechanisms were understood. A decerebrate cat, whose brain stem has been cut through, exhibits a phenomenon known as decerebrate rigidity. The animal’s back is arched, and its legs are extended Stiffly from its body. This rigidity results from excitation Originating in the caudal reticular formation, which greatly facilitates all stretch reflexes, especially of extensor muscles, by increasing the activity of the gamma motor system. Rostral to the brain stem transection is an inhibitory region of the reticular formation, which normally counterbalances the excitatory one. The transection removes the inhibitory influence, leaving only the excitatory one. If you attempt to flex the outstretched leg of a decerebrate cat, you will meet with increasing resistance, which suddenly melts away, allowing the limb to flex. It almost feels as though you were closing the blade of a pocket knife-hence the term clasp-knife reflex. The sudden release is, of course, mediated by activation of the Golgi tendon organ reflex.