The movements of the head—aside from those due to movements of the cervical spine—may be classified as those of flexion and extension; the bending forward and backward of the head; of rotation, in which the head remains erect; and of inclination or the depression of one or the other side. Flexion and extension of the head are of frequent necessity and physiological import; rotation is frequently necessary to move the eyes toward an object looked at, or to direct the ear toward a source of sound. Inclination is, I think, often of other significance: it sometimes indicates weakness, it is more frequently seen in young girls and weakly persons than in strong men. Inclination, with rotation to the same side, with slight flexion, is a position of the head very commonly seen in choreic girls, and then often accompanies an awkward, ill-balanced position of the spine. Inclination of the head, with rotation to the opposite side, and slight extension, is indicated by Sir Charles Bell in his figure in "Adoration." In seeking general information as to the signs of cerebral adequacy in an infant—that is, whether the infant has a good sound brain, probably capable of development—we always notice whether it can hold its head up, whether it usually keeps its head erect while sitting up.
Tooth-grinding, which is common in nervous children and among lunatics, champing of the jaws, and trismus, are signs of disordered conditions of the fifth nerve. The violent motions of the tongue seen in chorea and whooping-cough, the tremulous tongue of alcoholism and paralyses, indicate affections of the seventh nerve. Affections of the pneumogastric may produce palpitations, irregularities of organic action, the bronchial spasm of asthma, and functional aphasia.
It is a matter of very common experience that children and adult patients "hold themselves awkwardly"; stoop, or otherwise give the spine and trunk an ill-balanced position, due to want of nerve-muscular energy, and characteristic of the condition of exhaustion and weakness. Doubtless there is much expression in a torso; in many cases a weakly condition is indicated by a stooping attitude, with a lolling over to one side. It is difficult to indicate in precise terms the positions and movements of the spine, and perhaps this is one reason why so little is known about the action of the muscles of the back. With regard to the lower extremities, the gait and manner in walking may be characteristic of brain or cord disease. Conditions affecting the muscles of both lower extremities are usually dependent upon disease of the cord, and most of the signs by which spinal disease may be localized are derived from examination of the muscles of the legs. Reflex actions are also used as a means of localizing: and ascertaining the condition of the nerve-centers, and here, again, visible muscular conditions are the indices.
The significance of the action of muscles as indicating brain conditions has long been dwelt upon by writers. Camper, who wrote in 1821, has shown that the Laocoön presents evidence of how deeply the