Tensor tympani, a 'tuner' of tensor palati muscle.

The author has proved experimentally (in two dogs) that there is reflex hypertonia of the tensor palati muscle, synchronous with the 'shortening' reaction of the tensor tympani muscle in response to its "static" relaxation during the gradual passive inward displacement of the drum resulting from the negative intratympanic 'dip' due to absorption of air imprisoned within the middle ear. The author coined the term 'tuning' for the reflex hypertonia of tensor palati which is directly proportional to the degree of the slackness of its 'tuner', the muscle-tensor tympani. The degree of opening of the eustachian tube on swallowing depends upon the degree of 'tuning' of the tensor palati. The 'untuned' tensor palati fails to open the eustachian tube during swallowing. Presumably the excitation of tympanic chemoreceptors (glomus body) by the excess of CO2 during hypoxia of the tympanic cleft strengthens the 'shortening' reaction as well as the excitability of the tensor tympani muscle.