Notwithstanding this difficulty of classification, the troubles of respiration and phonation due to the complete or partial paralysis of the muscular apparatus are, for the convenience of study, divided into groups. These groups are based either upon the seat of the primary lesion or upon the kind of disturbance or the symptoms of the case. Neither method of grouping is satisfactory. We must content ourselves with a provisional arrangement. With the single exception of the arytenoideus, the muscles are double and symmetrical; paralysis may therefore be general or partial, unilateral or bilateral. The causes, symptoms, or terminations vary with this general or partial, double or single, character of the affection. We propose, therefore, to consider these motor derangements under the following heads, which in the main follow the classification of Mackenzie and most other writers upon the subject: 1. Paralysis of the whole larynx--of one-half of the larynx; {79} 2. Paralysis of the constrictors of the larynx; 3. Paralysis of the adductors of the vocal cords: _(a)_ unilateral, _(b)_ bilateral, _(c)_ central; 4. Paralysis of the tensors of the vocal cords: _(a)_ internal, _(b)_ external, _(c)_ unilateral, _(d)_ bilateral; 5. Paralysis of the abductors of the vocal cords, openers of the glottis: _(a)_ unilateral, _(b)_ bilateral. Paralysis of the Whole Larynx. Paralysis of all of the muscles of the larynx gives rise to a position of the parts which has, as before stated, been called the cadaveric condition. The vocal cords are neither abducted nor adducted. The opening of the glottis is sufficiently wide to admit of easy respiration, but the cords are so far apart as to make phonation impossible. The effort to articulate is not attended with any change in the position of the vocal bands. In respiration there is no additional widening of the glottic chink. The superior portion of the larynx is also in a peculiar condition. The epiglottis is erect, standing against the dorsum of the tongue; the vestibule of the larynx is widely open; deglutition is difficult.