Abstract
1. Guinea pigs blocked by intravenous injection of either India ink or trypan blue succumbed with fatal shock after the intravenous injection of heterophile immune serum, although the time of death was somewhat delayed as compared with normal controls. 2. Local blockade of the skin of guinea pigs with trypan blue inhibited completely the development of the characteristic skin reaction following intracutaneous injection of Forssman serum within the blocked area. 3. Infiltration of the skin of guinea pigs with India ink afforded no protection against the full development of the toxic skin reaction.