Responses of neurons in the supra-trigeminalis to sinusiodal jaw movements in the cat

A grass cutting head having a driving shaft mounting axially spaced flange and plate components. Angularly spaced collars re rotatably supported between the flange and plate components. Each collar is fabricated from a single unit having a slotted head portion and an integrally connected shank portion which is received in a corresponding aperture in the flange component. A radially extending nail is received in the slotted portion of each collar. The nail serves as a cutting bar and is maintained in the slotted portion by the plate component which is removably positioned against the slotted portion of the collar. The nails may be replaced by moving the plate component away from the slotted portion of the collar.