Abstract
An analysis has been made of the pattern of activity of the muscles of the head of the carp, in relation to respiratory movements and pressures generated in the buccal and opercular cavity, during normal respiration and during coughing. From comparison with the results of analyses carried out on other species of fish it is suggested that the respiratory movements of free-swimming teleosts in general conform to the following principles: the lateral expansions and contractions of the buccal and opercular cavities are always synchronous, but the lowering of the floor of the mouth may be synchronous with, or may precede, the lateral expansion. In the carp the levator operculi muscle, although it inserts on the opercular bone, does not participate in the opercular pump but is the abductor of the lower jaw.