“The muscles that connect the head with the thorax are contained within the prothorax (Fig. 232, 2), and are of three kinds, extensors, flexors, and retractors. The extensors, _levatores capitis_ (_a_, _a_), consist of two pairs, one of which arises from the middle line of the pronotum, and diverging laterally from its fellow of the opposite side, passes directly forwards, and is inserted by a narrow tendon into the anterior superior margin of the occipital foramen. The other arises further back from the prophragma. It is a long, narrow muscle that passes directly forwards through the prothorax, and is inserted by a tendon near the superior median line of the foramen; so that, while this muscle and its fellow of the opposite side elevate the head almost in a straight line, the one first described, when acting alone or singly, draws the head a little on one side; but when the whole of these muscles act in unison, they simply elevate the head upon the prothorax. The depressors or flexors, _depressores capitis_ (_b_), are exceedingly short muscles, which arise from the jugular plate, or, when that part does not exist, from the border of the prosternum, and are attached to the inferior margin of the occipital foramen. They simply flex the head on the prothorax. The lateral flexors, _depressores externi_ (_d_), are two little muscles that arise from the same point as the preceding, and are attached to the lateral inferior margin of the occipital foramen. The rotatory muscles, _rotatores capitis_ (_c_), are two flat muscles like the elevators, which arise, one at the side of the antefurca and the other from the posterior jugular plate, and passing upwards and outwards are attached to the lateral margin of the occipital foramen. The _retractor_ or flexor of the jugular plate is a small muscle (_e_) that arises from the margin of the antefurca, and passing directly forwards is inserted by a small tendon into the middle of the jugular piece. The _oblique extensor_ of the jugular plate is a long, slender muscle (_f_) that arises from the external margin of the pronotum, and passing obliquely downwards and forwards traverses the prothorax and is inserted by a narrow tendon to the jugular plate immediately before the retractor. The other retractor (_g_) arises from the anterior superior boundary of the pronotum, and passing downwards is inserted into the jugular plate between the larger levator and _flexor capitis_.