Both physiological and morphological studies revealed that cat tail muscles contain at least one pair of Golgi tendon organs innervated by branches of a single axon. 2. Fifteen pairs of such organs were subjected to physiological studies. It was found that, depending on the experimental conditions, two modes of interaction, 'resetting' and 'impulse mixing' may occur between impulse activities originating from individual tendon organs. 3. When a single action potential was elicited from one of a pair of Golgi tendon organs during an interimpulse interval of a train of impulse discharge originating from the partner organ, the subsequent impulses in the train were delayed ('resetting'). Similarly, if both organs were stimulated individually by a mechanical pulse to elicit a train of discharge, then during stimulation of both, only the response of one responding with higher frequency discharge was seen in the parent axon, the impulse activity of the partner organ being completely suppressed during this period. 4. Using the conditioning-test technique it was demonstrated that the initiation of an action potential in one of a pair of Golgi tendon organs caused a significant decrease in excitability of the partner organ to mechanical stimulation. 5. Mixing of impulse discharges originating from individual Golgi tendon organs was shown to occur during stimulation of both by suprathreshold short mechanical pulses. 6. The functional implication of the above results has been discussed.
